Suppressibility of Parathyroid Hormone in Primary Hyperparathyroidism

ObjectiveTo describe an unusual case of pathologically confirmed primary hyperparathyroidism in a patient presenting with severe hypercalcemia and an undetectable parathyroid hormone (PTH) level.MethodsWe present a detailed case report and outline the serial laboratory findings. In addition, the possible causes of low serum PTH levels in the setting of primary hyperparathyroidism are discussed.ResultsA 16-year-old female patient presented with severe epigastric pain, found to be attributable to acute pancreatitis. At hospital admission, her serum calcium concentration was high (14.0 mg/dL); the patient also had a normal serum phosphorus level of 3.6 mg/dL and an undetectable PTH level (< 0.2 pmol/L). An evaluation for non-PTH-mediated causes of hypercalcemia revealed a partially suppressed thyroid-stimulating hormone concentration and a below normal 1,25-dihydroxyvitamin D level, consistent with her suppressed PTH. One week after the patient was dismissed from the hospital, repeated laboratory studies showed a serum calcium value of 11.1 mg/dL, a serum phosphorus level of 2.8 mg/dL, and an elevated PTH concentration of 11.0 pmol/L, consistent with primary hyperparathyroidism. A repeated 1,25-dihy-droxyvitamin D measurement was elevated. A parathyroid scan showed a parathyroid adenoma in the left lower neck area, and she subsequently underwent successful surgical resection of a pathologically confirmed parathyroid adenoma.ConclusionThis case demonstrates that the serum PTH level can be suppressed in patients with primary hyperparathyroidism. Moreover, it emphasizes the need for careful evaluation of the clinical context in which the PTH measurement is determined. Consideration should be given to repeating measurement of PTH and serum calcium levels when the initial laboratory evaluation of hypercalcemia is unclear because dynamic changes in calcium metabolism may occur in the presence of secondary contributing factors. (Endocr Pract. 2007;13:785-789)     

Safety of Vitamin D Replacement in Patients with Primary Hyperparathyroidism and Concomitant Vitamin D Deficiency

ObjectiveTo evaluate the safety of vitamin D replacement in patients with vitamin D deficiency and primary hyperparathyroidism.MethodsRetrospective chart review of 35 patients from our endocrine clinic, age 22 to 89 years, diagnosed with primary hyperparathyroidism and vitamin D deficiency, and treated with either 1,000 to 2,000 international units (IU) of vitamin D daily or 50,000 IU of vitamin D weekly for 5 months. Data were collected before and after treatment on serum calcium, 25-hydroxyvitamin D (25-OH D), intact parathyroid hormone (iPTH), phosphorus, alkaline phosphatase, nephrolithiasis, fractures, and osteoporosis.Results25-OH D increased significantly, from a baseline of 14.65 ± 6.57 ng/mL to 42.17 ± 12.98 ng/ mL after weekly treatment with 50,000 IU of vitamin D (P<.0001), and from 22.42 ± 5.47 ng/mL to 33.33 ± 6.39 ng/mL following daily treatment with 1,000 to 2,000 IU of vitamin D (P<.0001). Pre- and posttreatment unadjusted serum calcium remained stable in the high-dose group (10.80 ± 0.43 mg/dL vs. 10.72 ± 0.67 mg/dL; P = .47), but decreased slightly in the low-dose group (10.76 ± 0.58 mg/dL vs. 10.11 ± 0.54 mg/dL; P = .0007). After adjusting for age, sex, vitamin D, and PTH levels, the small calcium difference in the low-dose group became statistically insignificant. Treatment with either high or low doses of vitamin D did not significantly change iPTH levels. Creatinine remained stable in all patients, and no new cases of nephrolithiasis were reported.ConclusionReplacing vitamin D in mild primary hyperparathyroidism is safe, effective, and does not increase calcium to dangerous levels. (Endocr Pract. 2013;19:420-425)     

Radioimmunoassay of Parathyroid Hormone in Primary Hyperparathyroidism: Studies after Removal of Parathyroid Adenoma

Parathyroid hormone has been measured by radioimmunoassay in eight patients with hyperparathyroidism due to parathyroid adenoma. Secretion of hormone by the adenomatas was demonstrated direct by estimating the arteriovenous gradient of parathyroid hormone across the tumours. Serial estimations following surgical removal of the adenoma showed a rapid fall in the concentration of circulating parathyroid hormone. The calculated half-life of endogenously secreted parathyroid hormone in man varied from 11·4 to 28·8 min., with a mean of 19·8 min.     

Preoperative Calcium and Parathyroid Hormone Values Are Poor Predictors of Gland Volume and Multigland Disease in Primary Hyperparathyroidism: A Review of 2000 Consecutive Patients

ObjectiveCalcium and parathyroid hormone (PTH) values are believed to have a linear relationship in patients with primary hyperparathyroidism and correlate with parathyroid gland size, with higher values predicting single-gland disease. In this modern series, these preoperative values were correlated with operative findings to determine their utility in predicting the gland involvement at parathyroid exploration.MethodsTwo thousand consecutive patients who underwent initial surgery for sporadic primary hyperparathyroidism from 2000 to 2014 were reviewed. All patients underwent a 4-gland exploration. Relationships between preoperative calcium and PTH values with the total gland volume of each patient were examined and stratified using the number of involved glands: single adenoma (SA), double adenoma (DA), and hyperplasia (H).ResultsThere were 1274 (64%) SA, 359 (18%) DA, and 367 (18%) H cases. There was a poor correlation between preoperative calcium and PTH values (R = 0.37) and both poorly correlated with the total gland volume (R < 0.40). Similarly, subgroup analysis using the number of involved glands showed poor correlation. The mean total gland volume was similar among all subgroups (SA = 1.28 cm³, DA = 1.43 cm³, and H = 1.27 cm³; P = .52), implying that individual glands were smaller in multigland disease. SA was found in 271 (53%) of patients with calcium levels of ≤10.5 mg/dL and 122 (78%) with levels of ≥12 mg/dL (P < .001).ConclusionThis is the largest series correlating preoperative calcium and PTH values with operative findings of gland size and number of diseased glands. Although a lower calcium value predicts somewhat more multigland disease, the overall poor correlation should make the parathyroid surgeon aware that gland size and multigland disease cannot be predicted by preoperative laboratory testing.     

Associations of Serum Ionized Calcium,Phosphate, and Pth Levels with Parathyroid Scan in Primary Hyperparathyroidism

Objective: To evaluate the relationship between various biochemical parameters in patients with primary hyperparathyroidism (PHPT) with positive and negative technetium-99 sestamibi (Tc) parathyroid scans performed with single-photon emission computed tomography/computed tomography (SPECT/CT).Methods: This retrospective analysis was used to develop a logistic probability model. It included 218 patients with PHPT. The main outcome measures were serum total calcium, ionized calcium, intact parathyroid hormone (PTH), albumin, alkaline phosphatase, phosphate, 25-hydroxy vitamin D, 1,25-dihydroxy vitamin D, 24-h urinary calcium levels, and parathyroid adenoma weight.Results: Individually, using cut-off levels of 6.0 mg/dL for ionized calcium, 3.0 mg/dL for phosphate, and 90 pg/mL for intact PTH, we found that 91.3% (P = .005), 70.7% (P = .004) and 87.90% (P = .023) of the patients had a positive Tc scan with their corresponding strengths of associations in the parentheses. Similar significant associations were sustained in multivariate setting for serum ionized calcium (P = .015), phosphate (P = .016), and intact PTH (P = .028). A logistic probability model was designed to predict the probability of being positive for Tc scan given a set of covariates.Conclusion: There are significant associations between the levels of serum ionized calcium, phosphate, intact PTH, and Tc scan positivity. Further studies with larger patient populations are needed.Abbreviations: BMI = body mass index; CT = computed tomography; CV = coefficient variation; DXA = dual-energy x-ray absorptiometry; MRI = magnetic resonance imaging; PHPT = primary hyperparathyroidism; PPV = positive predictive value; PTH = parathyroid hormone; SPECT = single-photon emission computed tomography; Tc = technetium-99 sestamibi     

Vitamin D-Binding Protein Levels in Female Patients with Primary Hyperparathyroidism

ObjectiveTo determine whether low levels of vitamin D-binding protein (DBP) are related to 25-hydroxyvitamin D (25[OH]D) deficiency in female patients with primary hyperparathyroidism (PHPT).MethodsTwenty-five female patients with PHPT (serum calcium level >10.2 mg/dL and intact parathyroid hormone (iPTH) level >66 pg/mL) and 25 healthy age- and body mass index-matched female control subjects were xaminod. Serum calcium and iPTH levels were determined by commercial laboratories. Levels of 25(OH)D and 1,25-dihydroxyvitamin D (1,25[OH]₂D) were determined by radioimmunoassay, and DBP level was determined by enzyme-linked immunosorbent assay.ResultsSerum iPTH and calcium levels were higher in PHPT patients than control subjects (P<.001). Levels of 25(OH)D, albumin, and DBP were lower in the serum of PHPT patients than control subjects (P<.01). There were no significant differences in 1,25(OH)₂D and free 25(OH) D levels between PHPT patients and control subjects. DBP level was inversely correlated with calcium (r = -0.47; P<.01) and iPTH (r = −0.31; P<.05) levels. The 25(OH)D level correlated positively with both DBP (r = 0.28; P <.05) and albumin (r = 0.44; P<.05) levels.ConclusionsBoth serum 25(OH)D and DBP levels were lower in female patients with PHPT compared with control subjects. We suggest that a low DBP level contributes to the low 25(OH)D level observed in female PHPT patients. The etiology of the decrease in DBP and its relationship to calcium, 25(OH)D, and PTH levels require further investigation. (Endocr Pract. 2013;19:609-613)     

KDIGO Categories of Glomerular Filtration Rate and Parathyroid Hormone Secretion in Primary Hyperparathyroidism

Objective: The recent Fourth Workshop on the Management of Asymptomatic primary hyperparathyroidism (PHPT) maintained the threshold of 60 mL/min for decreased renal function, below which surgery is recommended. This study investigated the relationship between different stages of renal insufficiency and parathyroid hormone (PTH) levels in an updated case series of PHPT patients.Methods: This was a retrospective, cross-sectional study involving 379 consecutive PHPT patients. Biochemical evaluation included total and ionized serum calcium, phosphate, creatinine, immunoreactive intact PTH, and 25-hydroxyvitamin D₃ (25[OH]D₃) levels in the fasting state. Glomerular filtration rate (GFR) was estimated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation.Results: Mean CKD-EPI estimated GFR was 81.9 ± 20.3 mL/min/1.73 m², and median GFR was 84.0 mL/min/1.73 m² (interquartile range, 26.8 mL/min/1.73 m²). The patients were divided into 5 groups according to the Kidney Disease: Improving Global Outcomes 2012 guidelines: group 1 with normal or increased GFR (>90 mL/min/1.73 m²); group 2 with mild GFR decrease (60 to 89 mL/min/1.73 m²); group 3a with mild to moderate GFR decrease (45 to 59 mL/min/1.73 m²); group 3b with moderate to severe GFR decrease (30 to 44 mL/min/1.73 m²); and group 4 with severe GFR decrease (<30 mL/min/1.73 m²). Among the 5 groups of patients, serum calcium levels were different (P = .025), whereas 25(OH)D₃ levels were not (P = .36). PTH levels were comparable across groups 1 through 3a, but they were significantly higher in groups 3b and 4 (P<.0001).Conclusion: In our series of PHPT patients, PTH levels did not rise as a result of renal impairment until GFR decreased below 45 mL/min/1.73 m².Abbreviations: 25(OH)D₃ = 25-hydroxyvitamin D₃ CKD-EPI = Chronic Kidney Disease-Epidemiology Collaboration GFR = glomerular filtration rate K/DOQI = National Kidney Foundation Disease Outcomes Quality Initiative KDIGO = Kidney Disease: Improving Global Outcomes MDRD = Modification of Diet in Renal Disease PHPT = primary hyperparathyroidism PTH = parathyroid hormone     

Primary Hyperparathyroidism and Vitamin D In African Americans

ObjectivesVitamin D deficiency is more common in African Americans than in the general population or other ethnicities. Vitamin D deficiency also occurs more frequently in patients with primary hyperparathyroidism (PHPT) than in the general population. Currently, the limited data on vitamin D deficiency in African Americans with primary hyperparathyroidism (PHPT) is inconsistent as to whether the vitamin D deficiency observed in PHPT is yet even more pronounced in Africans with PHPT relative to non-African Americans with PHPT.MethodsOn the basis of biochemical, radiological, and surgical (adenoma weight) parameters, African Americans have been reported to have a more severe form of PHPT than non-African Americans. However, comparative clinical manifestations of PHPT in African Americans have not been well described.ResultsCurrent guidelines recommend vitamin D repletion in mild, asymptomatic PHPT when levels of 25-hydroxyvitamin D are less than 20 ng/mL. Studies that reported vitamin D repletion with ergocalciferol or cholecalciferol in PHPT have not stratified data according to ethnicity. Discrepancies therefore exist between repleting vitamin D in African Americans who may potentially have a more severe PHPT profile, but simultaneously a more pronounced vitamin D deficiency.ConclusionEffectively designed clinical trials are necessary to evaluate the indications, efficacy, and safety of vitamin D in African Americans with PHPT. (Endocr Pract. 2012;18:947-953)     

Characteristics of Ectopic Parathyroid Glands in 145 Cases of Primary Hyperparathyroidism

ObjectiveTo determine the prevalence of primary hyperparathyroidism (PHPT) arising from ectopic parathyroid glands, to analyze the clinical, biochemical, and anatomic characteristics of such cases, and to compare these characteristics with those found in PHPT associated with orthotopic parathyroid glands.MethodsWe conducted a retrospective study of cases of PHPT evaluated and treated at a referral center. Differences between patients with orthotopic and ectopic parathyroid glands were analyzed statistically.ResultsDuring a recent 5-year period at our institution, 145 cases of PHPT were treated operatively by 3 experienced surgeons. An ectopic parathyroid location was detected in 13 cases (9%). Of the 13 ectopic glands, 4 (31%) were at the tracheoesophageal groove, 4 (31%) were intrathymic, 2 (15%) were intrathyroidal, and 1 each was located in the aortopulmonary window, the anterior (nonthymic) mediastinum, and the submaxillary region. Patients with PHPT attributable to ectopic adenomas had significantly higher serum calcium levels (12.6 ± 0.9 mg/ dL versus 11.4 ± 1.2 mg/dL; P = .05) and larger tumors (25 ± 6.1 mm versus 19 ± 7.6 mm; P = .05) than did patients with orthotopic parathyroid glands. Moreover, hyperparathyroidism-related bone disease was significantly more frequent in patients with abnormal ectopic parathyroid glands than in those with orthotopic parathyroid glands (23% versus 1.5%, respectively; P = .04).ConclusionIn 9% of all cases of PHPT in our study, the condition was associated with ectopically located parathyroid glands. Such cases are usually characterized by larger parathyroid glands, higher serum calcium levels, and a higher frequency of severe bone disease. (Endocr Pract. 2010;16:977-981)     

Vitamin D,Parathyroid Hormone,and Heart Failure in A Chinese Elderly Population

ObjectiveHeart failure (HF) is a major cause of morbidity and mortality worldwide. Low vitamin D status has been shown to be associated with increased risk of developing cardiovascular disease. In this study, we examined the association between vitamin D and parathyroid hormone (PTH) levels and HF in and elderly population in China.MethodsA population-based cross-sectional study was conducted in the spring of 2013 among 2,047 community-dwelling healthy individuals, aged 60 to 101 years. 25-Hydroxyvitamin D (25[OH]D) was measured using a chemiluminescence assay. PTH levels were measured with an electrochemiluminescence immunoassay.ResultsA total of 2,047 participants, including 1,121 women (54.7%), were evaluated in 2013. The median concentrations of serum 25(OH)D and PTH for the entire group were 16.1 ng/mL and 41.5 pg/mL, respectively. Serum 25(OH)D and PTH levels were associated with serum N-terminal pro-brain natriuretic peptide levels and left ventricular ejection fraction in a multivariate adjusted linear regression analysis (P < .05). In logistic regression analyses, serum 25(OH)D and PTH levels were associated with a risk of HF in single and multiple regression models (P < .05). Compared with patients with 25(OH)D levels between 30.0 and 44.9 ng/mL, patients with 25(OH)D levels less than 10 ng/mL had a higher mean hazard ratio for HF (2.88; 95% confidence interval, 1.59 to 4.38).ConclusionSerum 25(OH)D and PTH levels are independently associated with risk of HF in a Chinese elderly population. (Endocr Pract. 2014;21:30-40)     

Low Urine Calcium Excretion in African American Patients with Primary Hyperparathyroidism

ObjectiveTo evaluate the prevalence of low urine calcium excretion in African American patients with primary hyperparathyroidism (PHPT), a common disorder associated with bone and renal complications, and to assess the distinction between PHPT and familial hypocalciuric hypercalcemia (FHH), a rare benign genetic disease.MethodsWe conducted a retrospective study on a cohort of 1,297 patients in whom a 24-hour urine study was performed for measurement of urine calcium and creatinine. PHPT was diagnosed if the serum calcium concentration was ≥ 10.5 mg/dL and intact parathyroid hormone (PTH) was ≥ 40 pg/mL. Patients receiving medications that affect urine calcium or with glomerular filtration rate ≤ 30 mL/min were excluded.ResultsNinety-six patients satisfied the diagnostic criteria for PHPT. The African American (n = 70) and non-African American (n = 26) patients did not differ in their mean age, body mass index, glomerular filtration rate, serum PTH, 25-hydroxyvitamin D levels, and 24-hour urine creatinine values. Median values of urine calcium/creatinine (mg/g) were 122 for African American versus 214 for non-African American patients (P = .006). Thirty-one of 70 African American patients (44%) had a urine calcium/creatinine ratio ≤ 100 mg/g, whereas only 2 of 26 non-African American patients (8%) had this value (P = .001).ConclusionThe prevalence of low urine calcium excretion among African American patients with PHPT is unexpectedly high. A threshold of 100 mg/g urine calcium/ creatinine identified 44% of such patients with PHPT as having FHH in this cohort. Therefore, other clinical criteria and laboratory variables should be used to distinguish PHPT from FHH in African American patients with PTH-dependent hypercalcemia. (Endocr Pract. 2011;17: 867-872)     

The Vitamin D,Ionised Calcium and Parathyroid Hormone Axis of Cerebral Capillary Function: Therapeutic Considerations for Vascular-Based Neurodegenerative Disorders

Blood-brain barrier dysfunction characterised by brain parenchymal extravasation of plasma proteins may contribute to risk of neurodegenerative disorders, however the mechanisms for increased capillary permeability are not understood. Increasing evidence suggests vitamin D confers central nervous system benefits and there is increasing demand for vitamin D supplementation. Vitamin D may influence the CNS via modulation of capillary function, however such effects may be indirect as it has a central role in maintaining calcium homeostasis, in concert with calcium regulatory hormones. This study utilised an integrated approach and investigated the effects of vitamin D supplementation, parathyroid tissue ablation (PTX), or exogenous infusion of parathyroid hormone (PTH) on cerebral capillary integrity. Parenchymal extravasation of immunoglobulin G (IgG) was used as a marker of cerebral capillary permeability. In C57BL/6J mice and Sprague Dawley rats, dietary vitamin D was associated with exaggerated abundance of IgG within cerebral cortex (CTX) and hippocampal formation (HPF). Vitamin D was also associated with increased plasma ionised calcium (iCa) and decreased PTH. A response to dose was suggested and parenchymal effects persisted for up to 24 weeks. Ablation of parathyroid glands increased CTX- and HPF-IgG abundance concomitant with a reduction in plasma iCa. With the provision of PTH, iCa levels increased, however the PTH treated animals did not show increased cerebral permeability. Vitamin D supplemented groups and rats with PTH-tissue ablation showed modestly increased parenchymal abundance of glial-fibrillary acidic protein (GFAP), a marker of astroglial activation. PTH infusion attenuated GFAP abundance. The findings suggest that vitamin D can compromise capillary integrity via a mechanism that is independent of calcium homeostasis. The effects of exogenous vitamin D supplementation on capillary function and in the context of prevention of vascular neurodegenerative conditions should be considered in the context of synergistic effects with calcium modulating hormones.     

Parathyroid Carcinoma: An Experience from the Indian Primary Hyperparathyroidism Registry

ObjectiveTo describe the details of widely invasive parathyroid carcinoma (WIPC) patients admitted in the Endocrinology department of our institute during the last 22 years and to compare their clinical, biochemical, and hormonal profile with minimally invasive parathyroid carcinoma (MIPC) and sporadic parathyroid adenoma patients.MethodsThis is a retrospective analysis of data from the Indian primary hyperparathyroidism registry.ResultsOf the 547 primary hyperparathyroidism patients in the registry, 5 (2 men and 3 women) had WIPC (0.9%) and 7 (1 man and 6 women) had MIPC (1.3%), with median ages of 45 (interquartile range, 41-51) years and 47 (interquartile range, 28-48) years, respectively. Among the patients with WIPC, renal manifestations were present in 5 patients, skeletal manifestations in 4 patients, and palpable neck masses in 4 patients. Three patients had distant metastases and 2 had cervical lymph node involvement. All 5 patients had surgical resection of their cancers, with persistent disease in 4 patients, but all patients died within 2 years after surgery. One patient with MIPC had a palpable parathyroid nodule; none had lymph nodal or distant metastases. None of the patients with MIPC died during the median follow-up of 18 (interquartile range, 12-18) months. Patients with WIPC had significantly higher serum calcium level compared with sporadic parathyroid adenoma patients with skeletal and renal manifestations.ConclusionAccurate histopathologic classification of parathyroid carcinoma is important as WIPC is associated with a more aggressive clinical course and a higher risk of mortality than MIPC.     

Vitamin D,Parathyroid Hormone,and Serum Lipid Profiles in a Middle-Aged and Elderly Chinese Population

ObjectivesTo explore the associations of serum vitamin D and parathyroid hormone (PTH) levels with serum lipid profiles and the risk of hyperlipidemia in a middle-aged and elderly population.MethodsA population-based cross-sectional study was conducted in the spring of 2012 among 1,203 Chinese participants, aged 52 to 101 years. 25-Hydroxyvitamin D [25(OH)D] was measured by chemiluminescence assay. (PTH) levels were measured with an electrochemilumines-cence immunoassay (ECLIA) method.ResultsA total of 1,203 participants, including 526 women (43.7%), were evaluated in 2012. The median concentrations of serum 25(OH)D and PTH for the entire group were 17.3 ng/mL and 38.3 pg/mL, respectively. Serum 25(OH)D and PTH levels were not independently associated with serum total cholesterol, triglycerides, low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol levels in a multivariate adjusted linear regression analysis of 1,027 participants not receiving antihyperlipidemic treatment (P > .05). In logistic regression analyses, serum 25(OH)D and PTH lev-els were not associated with a risk of hyperlipidemia after adjustment for age, sex, heavy drinking, smoking, diabetes, obesity, family history of hyperlipidemia, body mass index (BMI), physical activity, glomerular filtration rate (GFR), fasting glucose, high-sensitivity Creactive protein (hsCRP), calcium, and hemoglobin.ConclusionsSerum 25(OH)D and PTH levels are not independently associated with serum lipid levels or an increased risk of hyperlipidemia in a middle-aged and elderly Chinese population. (Endocr Pract. 2014;20: 556-565)     

Temporal Relationship between Vitamin D Status and Parathyroid Hormone in the United States

Background

Interpretation of parathyroid hormone (iPTH) requires knowledge of vitamin D status that is influenced by season.

Objective

Characterize the temporal relationship between 25-hydroxyvitamin D₃ levels [25(OH)D₃] and intact iPTH for several seasons, by gender and latitude in the U.S. and relate 25-hydrovitamin D₂ [25(OH)D₂] levels with PTH levels and total 25(OH)D levels.

Method

We retrospectively determined population weekly-mean concentrations of unpaired [25(OH)D₂ and 25(OH)D₃] and iPTH using 3.8 million laboratory results of adults. The 25(OH)D₃ and iPTH distributions were normalized and the means fit with a sinusoidal function for both gender and latitudes: North >40, Central 32–40 and South <32 degrees. We analyzed PTH and total 25(OH)D separately in samples with detectable 25(OH)D₂ (≥4 ng/mL).

Findings

Seasonal variation was observed for all genders and latitudes. 25(OH)D₃ peaks occurred in September and troughs in March. iPTH levels showed an inverted pattern of peaks and troughs relative to 25(OH)D₃, with a delay of 4 weeks. Vitamin D deficiency and insufficiency was common (33% <20 ng/mL; 60% <30 ng/mL) as was elevated iPTH levels (33%>65 pg/mL). The percentage of patients deficient in 25(OH)D₃ seasonally varied from 21% to 48% and the percentage with elevated iPTH reciprocally varied from 28% to 38%. Patients with detectable 25(OH)D₂ had higher PTH levels and 57% of the samples with a total 25(OH)D > 50 ng/mL had detectable 25(OH)D₂.

Interpretation

25(OH)D₃ and iPTH levels vary in a sinusoidal pattern throughout the year, even in vitamin D₂ treated patients; 25(OH)D₃, being higher in the summer and lower in the winter months, with iPTH showing the reverse pattern. A large percentage of the tested population showed vitamin D deficiency and secondary hyperparathyroidism. These observations held across three latitudinal regions, both genders, multiple-years, and in the presence or absence of detectable 25(OH)D₂, and thus are applicable for patient care.     

Urinary Calcium Excretion in Primary Hyperparathyroidism: Relationship to 25-Hydroxyvitamin D Status

ObjectiveTo determine the prevalence of vitamin D deficiency in patients with primary hyperparathyroidism (PHPT) and evaluate the relationship between urinary calcium excretion and serum 25-hydroxyvitamin D (25-OH-D) levels in patients with PHPT.MethodsWe present a case report and a review of the medical records of patients with PHPT. Of 75 patients with PHPT substantiated by hypercalcemia and increased levels of intact parathyroid hormone (iPTH), 35 were identified with laboratory evaluation of vitamin D levels and 24-hour urinary calcium excretion. These study subjects were stratified as 25-OH-D deficient, insufficient, or replete (on the basis of serum values of < 15, 15 to 25, or > 25 ng/mL, respectively). Total 24-hour urinary calcium excretion and the fractional excretion of calcium (FECa) were analyzed as a function of 25-OH-D status.ResultsOf the 35 study subjects, 14 (40%) and 13 (37%) had 25-OH-D deficiency or insufficiency, respectively. Those patients with a 25-OH-D level < 15 ng/mL had higher serum iPTH concentrations as well as lower urinary calcium excretion and FECa. No significant correlations were found, however, between 25-OH-D status and iPTH concentrations (r = -0.21; P = 0.23), total 24-hour urinary calcium excretion (r = 0.07; P = 0.7), or FECa (r = 0.04; P = 0.8).ConclusionVitamin D deficiency (25-OH-D levels < 15 ng/mL) was common in our population of patients with PHPT. Urinary calcium excretion was not significantly altered by 25-OH-D deficiency in patients with newly recognized PHPT. Measurements of total urinary calcium excretion and FECa can be reliably used to rule out familial benign hypocalciuric hypercalcemia in the initial evaluation of PHPT, regardless of 25-OH-D status. Determining 25-OH-D concentrations best assesses the vitamin D status. (Endocr Pract. 2005;11:37-42)     

Increased Serum Calcium is not Common in Hospitalized Patients with Primary Hyperparathyroidism: A Retrospective,Observational Study

Objective: Serum calcium levels often decrease during acute illness in patients with an intact calcium-regulating system. However, the dynamics of serum calcium levels in hospitalized patients with primary hyperparathyroidism (PHPT) have not yet been described.Methods: Clinical and laboratory data were retrospectively retrieved from the electronic medical records of patients with PHPT before, during, and after hospitalization for various reasons (excluding parathyroid surgery).Results: There were 99 nonselected patients with asymptomatic, hypercalcemic PHPT, hospitalized for various reasons; 42% were admitted for apparent infectious or septic conditions, and 58% were admitted for noninfectious conditions. Total serum calcium increased >0.5 mg/dL in 7.4% of the patients: 10.9% and 2.5% of the patients with noninfectious and infectious conditions, respectively. In 65.7% of the patients, the mean total serum calcium (TsCa), but not albumin-corrected calcium (corrCa), decreased significantly during hospitalization, down to below the upper limit of the reference range. Although prehospitalization TsCa and corrCa were similar in patients with infectious and noninfectious conditions, during hospitalization, TsCa was lower in patients with infectious conditions (P = .02). Both TsCa and albumin returned to prehospitalization levels after recovery.Conclusion: TsCa increases in a minority of hospitalized PHPT patients. In the majority of hospitalized patients with PHPT, TsCa, but not corrCa, decreases to within the normal reference range, more so in patients with infectious conditions, obscuring the major characteristic of PHPT. Therefore, it is prudent to follow calcium and corrCa during hospitalization in patients with PHPT.Abbreviations: corrCa = albumin-corrected serum calcium; IQR = interquartile range; PHPT = primary hyperparathyroidism; PTH = parathyroid hormone; TsCa = total serum calcium     

Role of Imaging Tests for Preoperative Location of Pathologic Parathyroid Tissue in Patients with Primary Hyperparathyroidism

Objective: Primary hyperparathyroidism (PHPT) can be cured by parathyroidectomy, and the preoperative location of enlarged pathologic parathyroid glands is determined by imaging studies, especially cervical ultrasonography and scintigraphy scanning. The aim of this retrospective study was to evaluate the use of preoperative cervical ultrasonography and/or parathyroid scintigraphy in locating pathologic parathyroid tissue in a group of patients with PHPT followed in the same endocrine center.Methods: We examined the records of 61 patients who had undergone parathyroidectomy for PHPT following ^99mTc-sestamibi scintigraphy scan and/or cervical ultrasonography. Scintigraphic and ultrasonographic findings were compared to histopathologic results of the surgical specimens.Results: Ultrasonography detected enlarged parathyroid glands in 87% (48/55) of patients with PHPT and ^99mTc-sestamibi scintigraphy in 79% (37/47) of the cases. Ultrasonography was able to correctly predict the surgical findings in 75% (41/55) of patients and scintigraphy in 72% (34/47). Of 7 patients who had negative ultrasonography, scintigraphy correctly predicted the surgical results in 2 (29%). Of 10 patients who had negative scintigraphy, ultrasonography correctly predicted the surgical results in 4 (40%). When we analyzed only patients with solitary eutopic parathyroid adenomas, the predictive positive values of ultrasonography and scintigraphy were 90% and 86%, respectively.Conclusion: Cervical ultrasonography had a higher likelihood of a correct positive test and a greater predictive positive value for solitary adenoma compared to ^99mTc-sestamibi and should be used as the first diagnostic tool for preoperative localization of affected parathyroid glands in PHPT.Abbreviations:Ca = calciumIEDE = Instituto Estadual de Diabetes e Endocrinologia Luiz CapriglionePHPT = primary hyperparathyroidismPTH = parathyroid hormone     

Reduced Parathyroid Hormone-Stimulated 1,25-Dihydroxyvitamin D Production in Vitamin D Sufficient Postmenoposual Women with Low Bone Mass and Idiopathic Secondary Hyperparathyroidism

ObjectiveDistinguishing secondary hyperparathyroidism (sHPT) from eucalcemic primary hyperparathyroidism (EC-pHPT) is important. The objective of this study was to measure parathyroid hormone (PTH)-stimulated production of 1α,25-dihydroxyvitamin D (1,25[OH]₂D) in early postmenopausal patients with idiopathic sHPT, who also fit the criteria for EC-pHPT, compared to age-matched controls.MethodsIn this pilot case-control study, postmenopausal women aged 44 to 55 years with normal serum calcium (Ca), glomerular filtration rate (GFR) ≥65 mL/min, and 25-hydroxyvitamin D (25[OH]D) ≥75 nmol/L (30 ng/mL) were given an 8 hour infusion of PTH(1-34), 12 pmol/kg/h. Patients (n = 5) had elevated PTH, normal 1,25(OH)₂D, and no hypercalciuria. Controls (n = 5) had normal PTH. At baseline, 4, and 8 hours, serum Ca, creatinine (Cr), phosphorus (P), 1,25(OH)₂D, fibroblast growth factor (FGF23), and 24,25(OH)₂D as well as urine Ca, P, Cr, and cAMP/GFR were measured. The fractional excretion of calcium (FeCa) and tubular reabsorption of phosphorus (TMP)/GFR were calculated.ResultsPatients had lower 1,25(OH)₂D levels (± SD) than controls at 4 (39.8 ± 6.9 versus 58.8 ± 6.7; P = .002) and 8 hours (56.4 ± 9.2 versus 105 ± 2.3; P = .003) of PTH infusion, attenuated after adjusting for higher body mass index (BMI) in patients (P = .05, .04), respectively. The 24,25(OH)2D levels were lower in patients than controls (1.9 ± 0.6 versus 3.4 ± 0.6, respectively; P = .007). No differences were seen in serum Ca or P, urine cAMP/GFR, TRP/GFR, FeCa, or PTH suppression at 8 hours (patients 50%, controls 64%).ConclusionVitamin D sufficient patients who fit the criteria for EC-pHPT had reduced PTH-stimulated 1,25(OH)₂D compared to controls, partially attributable to their higher BMI. Other causes of reduced 1,25(OH)₂D production ruled out were excessive catabolism of vitamin D metabolites, elevated FGF23, and CYP27B1 mutation. Elevated BMI and idiopathic reduced PTH-stimulated 1,25(OH)₂D production should be considered in the differential of sHPT. (Endocr Pract. 2013;19:91-99)     

Vitamin D Status among Thai School Children and the Association with 1,25-Dihydroxyvitamin D and Parathyroid Hormone Levels

In several low latitude countries, vitamin D deficiency is emerging as a public health issue. Adequate vitamin D is essential for bone health in rapidly growing children. In the Thai population, little is known about serum 25-hydroxyvitamin D [25(OH)D] status of infants and children. Moreover, the association between 25(OH)D and the biological active form of 1,25-dihydroxyvitamin D [1,25(OH)]₂D is not clear. The specific aims of this study were to characterize circulating serum 25(OH)D, 1,25(OH)₂D and their determinants including parathyroid hormone (PTH), age, sex, height and body mass index (BMI) in 529 school-aged Thai children aged 6–14 y. Adjusted linear regression analysis was performed to examine the impact of age and BMI, and its interaction with sex, on serum 25(OH)D concentrations and 1,25(OH)₂D concentrations. Serum 25(OH)D, 1,25(OH)₂D and PTH concentrations (geometric mean ± geometric SD) were 72.7±1.2 nmol/L, 199.1±1.3 pmol/L and 35.0±1.5 ng/L, respectively. Only 4% (21 of 529) participants had a serum 25(OH)D level below 50 nmol/L. There was statistically significant evidence for an interaction between sex and age with regard to 25(OH)D concentrations. Specifically, 25(OH)D concentrations were 19% higher in males. Moreover, females experienced a statistically significant 4% decline in serum 25(OH)D levels for each increasing year of age (P = 0.001); no decline was seen in male participants with increasing age (P = 0.93). When BMI, age, sex, height and serum 25(OH)D were individually regressed on 1,25(OH)₂D, height and sex were associated with 1,25(OH)₂D with females exhibiting statistically significantly higher serum 1,25(OH)₂D levels compared with males (P<0.001). Serum 1,25(OH)₂D among our sample of children exhibiting fairly sufficient vitamin D status were higher than previous reports suggesting an adaptive mechanism to maximize calcium absorption.