Protein tyrosine sulfation in guinea-pig uterus: estradiol and progesterone effects

Tyrosine sulfation was studied in guinea-pig uterus by in vitro labelling with [35S]sulfate, after estradiol-17 beta (E2) and E2 plus progesterone (P) treatment. [35S]Sulfated tyrosine was identified in tissue and secreted proteins, ranged from 9.3 to 21.0% of total protein sulfation and was higher in secreted proteins than in tissue proteins. Sulfate incorporation into tyrosine increased with hormone treatments. The highest level was found in secreted proteins under the combined effect of E2 plus P. The effect of P may be related to both the increase of cellular uptake of sulfate and the increase of tyrosine sulfation of secreted proteins. These results are consistent with the effect of P on endometrium secretions.     

Pituitary glycoprotein hormone oligosaccharides: structure, synthesis and function of the asparagine-linked oligosaccharides on lutropin, follitropin and thyrotropin

Luteinizing hormone (LH), follicle-stimulating hormone (FSH) and thyroid-stimulating hormone (TSH) from pituitary and chorionic gonadotropin (CG) from placenta are a family of closely related glycoproteins. Each hormone is a heterodimer, consisting of an alpha- and a beta-subunit. Within an animal species, the alpha-subunits of all four glyco-protein hormones have an identical amino acid sequence, whereas each beta-subunit is distinct and confers hormone-specific features to the heterodimer. LH and FSH are synthesized within the same cell, the gonadotroph of the anterior pituitary, but are predominantly stored in separate secretory granules. We have characterized the asparagine-linked oligosaccharides on bovine, ovine and human LH, FSH and TSH. The various pituitary hormones were found to contain unique sulfated oligosaccharides with the terminal sequence SO4-4GalNAc beta 1----4GlcNAc beta 1----2Man alpha, sialylated oligosaccharides with the terminal sequence SA alpha Gal beta GlcNAc beta Man alpha, or both sulfated and sialylated structures. Despite synthesis of LH and FSH in the same pituitary cell, sulfated oligosaccharides predominate on LH while sialylated oligosaccharides predominate on FSH for all three animal species. We have examined the reactions leading to synthesis of the sulfated oligosaccharides to determine which steps are hormone specific. The sulfotransferase is oligosaccharide specific, requiring only the sequence GalNAc beta 1----4GlcNAc beta 1----2Man alpha. In contrast, the GalNAc-transferase appears to be protein specific, accounting for the preferential addition of GalNAc to LH, TSH, and free (uncombined) alpha-subunits compared with FSH and other pituitary glycoproteins. The predominance of sulfated oligosaccharide structures on LH may account for sorting of LH and FSH into separate secretory granules. Differences in sulfation and sialylation of LH, FSH and TSH may also play a role in the regulation of hormone bioactivity.     

Development of Low-Molecular-Weight Allosteric Agonist of Thyroid-Stimulating Hormone Receptor with Thyroidogenic Activity

Doklady Biochemistry and Biophysics - To normalize the thyroid status in hypothyroidism caused by resistance to thyroid-stimulating hormone (TSH), low-molecular-weight allosteric agonists of TSH...     

Sulfation and sialylation requirements for a glycoform of CD34, a major endothelial ligand for L-selectin in porcine peripheral lymph nodes

Leukocyte recruitment from blood into peripheral lymph nodesis controlled in part by a specific interaction of lymphocyte-associatedL-selectin with endothelial cell receptors known as peripheraladdressins. In murine lymph nodes, two peripheral addressinshave been identified, GlyCAM-1, a 50 kDa molecule that alsoappears as a secreted form in plasma, and CD34, a 90 kDa membrane-associatedsialomucin. A predominant 105 kDa CD34 mucin-like protein hasalso been identified in human tonsil as peripheral addressin.We have identified a 120 kDa sialomucin as the predominant peripheraladdressin in porcine lymph nodes. Validation of the 120 kDaporcine molecule as a peripheral addressin was based on itsability to bind MECA-79, a monoclonal antibody previously usedto isolate peripheral addressins from mouse and human tissues,and to bind an L-selectin-Fc chimera (LS-Fc). The binding withLS-Fc was abolished in the presence of fucoidin, a sulfatedpolysac-charide known to inhibit L-selectin-receptor interactions.To address the possibility that the 120 kDa ligand may containcommon recognition determinants for MECA-79 and L-selectin,the requirements for sialylation and sulfa-tion were compared.Whereas desialylation of 120 kDa ligand drastically reducedits binding to LS-Fc, this treatment appeared to enhance thebinding of 120 kDa ligand to MECA-79. In contrast, the bindingof both MECA-79 and LS-Fc to 120 kDa ligand was drasticallyreduced when de novo sulfation of this ligand was reduced byincluding chlorate, a metabolic inhibitor of sulfation, in theculture media. N-Terminal amino acid sequences of the porcine120 kDa protein revealed homology with human CD34. Taken together,these findings suggest that the porcine 120 kDa peripheral addressinis an L-selectin-binding glyco-form of CD34. L-selectin sulfation sialylation CD34 inflam-mation     

Grades of Hypothyroidism

Seventy-nine patients with hypothyroidism and autoimmune thyroid disease were studied, and allotted to one of four categories on the basis of clinical and biochemical features. Firstly, patients with overt hypothyroidism had obvious clinical features of hypothyroidism and abnormal results from routine tests of thyroid function. Secondly, those with mild hypothyroidism, however, had minor and non-specific symptoms, but the routine measurements of circulating thyroid hormone concentration generally lay within the normal range, although they were significantly lower than those seen in subclinical hypothyroidism or in normal subjects. The serum concentration of thyroid-stimulating hormone (TSH) was raised in this group and their symptoms resolve with treatment. Thirdly, patients with subclinical hypothyroidism were asymptomatic, had a raised serum TSH concentration, but all other measurements of thyroid function are indistinguishable from those recorded in people with autoimmune thyroid disease without disturbance of thyroid function and in normal subjects. Lastly, subjects with circulating thyroid antibodies, normal indices of thyroid function, and a normal serum TSH concentration were indistinguishable biochemically from normal subjects.Thus hypothyroidism is a graded phenomenon, the most valuable features for defining the individual grade being the clinical manifestations, the serum TSH concentration, and the presence of circulating antibodies to thyroid tissue.     

Asparagine-linked oligosaccharides on lutropin, follitropin, and thyrotropin. I. Structural elucidation of the sulfated and sialylated oligosaccharides on bovine, ovine, and human pituitary glycoprotein hormones

We have elucidated the structures of the anionic asparagine-linked oligosaccharides present on the glycoprotein hormones lutropin (luteinizing hormone), follitropin (follicle-stimulating hormone), and thyrotropin (thyroid-stimulating hormone). Purified hormones, isolated from bovine, ovine, and human pituitaries, were digested with N-glycanase, and the released oligosaccharides were reduced with NaB[3H]4. The 3H-labeled oligosaccharides from each hormone were then fractionated by anion-exchange high performance liquid chromatography (HPLC) into populations differing in the number of sulfate and/or sialic acid moieties. The anionic oligosaccharides were further purified as well as structurally characterized using a variety of preparative and analytical techniques, including HPLC, endo- and exoglycosidase digestions, and lectin affinity chromatography. The sulfated, sialylated, and sulfated/sialylated structures, which together comprised 67-90% of the asparagine-linked oligosaccharides on the pituitary glycoprotein hormones, were highly heterogeneous and displayed hormone- as well as animal species-specific features. The sulfated oligosaccharides consisted of hybrid and complex type oligosaccharides with one or two branches terminating in SO4-4GalNAc beta 1,4. In contrast, the sialylated oligosaccharides consisted of a wide array of differing structures containing two or three peripheral branches as well as one, two, or three sialic acid moieties. A previously uncharacterized dibranched oligosaccharide, bearing one residue each of sulfate and sialic acid, was found on all of the hormones except bovine lutropin. In this study, we describe the purification and detailed structural characterizations of the sulfated, sialylated, and sulfated/sialylated oligosaccharides found on lutropin, follitropin, and thyrotropin from several animal species. In the accompanying paper (Green, E.D., and Baenziger, J.U.(1987) J. Biol. Chem. 262, 36-44) we demonstrate the marked quantitative differences among the pituitary glycoprotein hormones in terms of sulfation, sialylation, and underlying oligosaccharide structures, as well as provide evidence for site-specific synthesis of oligosaccharides on individual hormones.     

Postpartum Levothyroxine Adjustment and Its Impact Factors in Women With Hypothyroidism in Pregnancy

ObjectiveWomen with hypothyroidism need to increase exogenous thyroid hormone levels during pregnancy to reduce adverse outcomes. Few studies have reported the effect of gestational levothyroxine (LT4) variations on postpartum LT4 treatment.MethodsWomen were classified as having subclinical hypothyroidism (SCH) (n = 101), overt hypothyroidism (OH) caused by autoimmune thyroiditis (AIT-OH), OH following thyroidectomy for benign thyroid disease (BA-OH) (n = 66), and OH after surgery for papillary thyroid cancer (PTC-OH) (n = 46). Thyroid function was monitored, and LT4 therapy was adjusted accordingly.ResultsAfter delivery, all women with SCH stopped LT4 treatment, and 57.4% of them restarted LT4 treatment in the following 1 year, independently of the gestational LT4 variations. Among patients with OH, after adjusted by gestational body weight, 49.1% of them had LT4 doses less than the prepregnancy dose (baseline) in late pregnancy, leading to LT4 reduction in postpartum. The LT4 dose was reduced to approximately 50% baseline for women with AIT-OH and BA-OH and reduced by 27% for women with PTC-OH. The reduction reasons for AIT-OH and BA-OH were thyroid-stimulating hormone levels of <2.5 mU/L during pregnancy and postpartum thyrotoxicosis occurrence (39.4%), and for PTC-OH, the reason was thyroid-stimulating hormone overinhibition (<1.0 mU/L) before delivery.ConclusionFor patients with SCH, postpartum LT4 treatment could initially be suspended. For women with OH, if the LT4 dose in late pregnancy was less than baseline, a prepregnancy dose reduced by 50%, 50%, and 27% should be applied after delivery for women with AIT-OH, BA-OH, and PTC-OH, respectively.     

Predictors of Hypothyroidism Following Empirical Dose Radioiodine in Toxic Thyroid Nodules: Real-Life Experience

ObjectiveWe aimed to determine the factors predicting hypothyroidism after radioactive iodine (RAI) treatment in patients with toxic adenoma and toxic multinodular goiter.MethodsWe retrospectively collected the data of 237 patients with toxic multinodular goiter or toxic adenoma who had consecutively received RAI treatment between 2014 and 2020 at 2 medical centers. Patients who received the second RAI treatment and whose medical records could not be accessed were excluded from the study. Finally, 133 patients were included in the study. RAI was administered at an empirical dose of 15 or 20 mCi.ResultsThe median age of the 133 participants was 69 years (interquartile range, 62-75 years), and 64.7% of the participants were women. A total of 42.1% of the patients had toxic adenoma, whereas 57.9% of patients had toxic multinodular goiter. The median follow-up was 24 months (interquartile range, 11-38 months). During the follow-up, 61.7% of patients became euthyroid, 30.8% developed hypothyroidism, and 7.5% remained hyperthyroid. The median month of hypothyroidism onset was 4 months (interquartile range, 2-9 months). Regression analysis revealed 2 factors that could predict hypothyroidism: thyroid-stimulating hormone (odds ratio, 2.548; 95% CI, 1.042-6.231; P = .04) and thyroid volume (odds ratio, 0.930; 95% CI, 0.885-0.978; P = .005).ConclusionOverall, 30.8% of the cases developed hypothyroidism after the RAI treatment. Approximately 78% of hypothyroidism developed within the first 10 months. The risk of hypothyroidism was higher in patients with higher thyroid-stimulating hormone and smaller thyroid volume.     

Thyroid-stimulating hormone receptor in brown adipose tissue is involved in the regulation of thermogenesis

C.RF- Tshr(hyt/hyt) mice have a mutated thyroid-stimulating hormone receptor (TSHR), and, without thyroid hormone supplementation, these mice develop severe hypothyroidism. When hypothyroid Tshr(hyt/hyt) mice were exposed to cold (4 degrees C), rectal temperature rapidly dropped to 23.9 +/- 0.40 degrees C at 90 min, whereas the wild-type mice temperatures were 37.0 +/- 0.15 degrees C. When we carried out functional rat TSHR gene transfer in the brown adipose tissues by plasmid injection combined with electroporation, there was no effect on the serum levels of thyroxine, although rectal temperature of the mice transfected with pcDNA3.1/Zeo-rat TSHR 90 min after cold exposure remained at 34.6 +/- 0.34 degrees C, which was significantly higher than that of Tshr(hyt/hyt) mice. Transfection of TSHR cDNA increased mRNA and protein levels of uncoupling protein-1 (UCP-1) in brown adipose tissues, and the weight ratio of brown adipose tissue to overall body weight also increased. Exogenous thyroid hormone supplementation to Tshr(hyt/hyt) mice restored rectal temperature 90 min after exposure to cold (36.8 +/- 0.10 degrees C). These results indicate that not only thyroid hormone but also thyroid-stimulating hormone (TSH)/TSHR are involved in the expression mechanism of UCP-1 in mouse brown adipose tissue. TSH stimulates thermogenesis and functions to protect a further decrease in body temperature in the hypothyroid state.     

Familial hypothyroidism caused by a nonsense mutation in the thyroid-stimulating hormone beta-subunit gene.

Hereditary hypothyroidism caused by thyroid-stimulating hormone (TSH) deficiency is a rare autosomal recessive disease. Affected individuals show symptoms of severe mental and growth retardation that can be prevented by early administration of exogenous thyroid hormone. In this paper, we describe two related Greek families with three children affected by congenital TSH-deficient hypothyroidism. Sequence analysis of the TSH beta-subunit gene (TSHB) showed that the mutation responsible for the hypothyroidism in these families is a nonsense mutation in exon 2. This mutation is a G-to-T transversion at nucleotide 94 that destroys the only TaqI site in the TSHB-coding region and gives rise to a novel 8.5-kb TaqI fragment. Restriction analysis showed that the three affected children are homozygous for the 8.5-kb allele and that the four parents and two unaffected children are heterozygous. This mutation gives rise to a truncated peptide which includes only the first 11 of 118 amino acids of the mature TSHB peptide.     

In vitro sulfation of pulmonary surfactant-associated protein-35

Surfactant-associated protein-35 consists of a group of phospholipid-associated proteins of 26-36 kDa isolated from pulmonary alveolar surfactant. In the rat, surfactant-associated protein-35 is synthesized from 26-kDa primary translation products which are cotranslationally acetylated and glycosylated to heterogeneous 30 and 34 kDa forms. High-mannose oligosaccharide-containing precursors of surfactant-associated protein-35 are processed in the rough endoplasmic reticulum and Golgi to complex-type oligosaccharides, resulting in a mature glycoprotein which exhibits extensive charge heterogeneity in two-dimensional isoelectric focusing SDS-polyacrylamide gel electrophoresis. Much of this charge heterogeneity is related to terminal sialylation of the two asparagine-linked oligosaccharides. In the present study, we report that surfactant-associated protein-35 is also sulfated. Sulfation of the 30 and 34 kDa forms of surfactant-associated protein-35 was clearly detected in primary cultures of rat Type II epithelial cells. These sulfated isoforms were sensitive to endoglycosidase F digestion, but resistant to neuraminidase, suggesting that sulfation occurred at oligosaccharide residues other than sialic acid. The lack of sulfation of the 26 kDa forms of surfactant-associated protein-35 and the resistance of the sulfated isoforms to endoglycosidase H digestion are consistent with Golgi-associated sulfation of the complex type oligosaccharides of surfactant-associated protein-35. Thus, sulfation is another component of the complex post-translational processing of surfactant-associated protein-35, which includes acetylation, hydroxylation, glycosylation, sialylation, sulfhydryl-dependent oligomerization and sulfation.     

Population screening for congenital hypothyroidism.

A pilot screening programme for congenital hypothyroidism covering most of North London, Essex, Bedfordshire, and Hertfordshire entailed carrying out an assay of thyroid-stimulating hormone on single Guthrie dried blood spots. During one year 87 444 babies were screened and 26 cases of primary congenital hypothyroidism detected, giving an incidence of 1:3363. Only two cases (7.7%) had already been diagnosed on clinical grounds before the results of screening became available. In two other babies the diagnosis was delayed. The programme thus resulted in the early treatment of 22 babies, eight of whom already had pronounced features of hypothyroidism that had not been detected on routine clinical examinations. Although definitive evidence will not be available for some years, the results suggest that the prognosis for most of these babies is likely to be improved by early diagnosis; thus the introduction of national screening should be delayed no longer.     

Therapeutic exploration of betulinic acid in chemically induced hypothyroidism

Hypothyroidism is a chronic condition characterized by abnormally low thyroid hormone production. The decreased serum level (>5.1 mIU/l) of thyroid-stimulating hormone (TSH) in blood indicates hypothyroidism. The study was an attempt to access the effect of betulinic acid on chemically induced hypothyroidism in female albino rats. Betulinic acid is a naturally occurring pentacyclic triterpenoid, which has antiretroviral, antimalarial, and anti-inflammatory properties, as well as anticancer potential, by inhibiting topoisomerase. Hypothyroidism was induced in female albino rats using propylthiouracil (PTU) at a dose of 60 μg/kg body weight orally for 1 month. Induction of hypothyroidism was confirmed by increased TSH level. At the end of second month, blood was collected, centrifuged and serum was analyzed for TSH, T3, and T4 level and protocol was terminated by killing of animals. The animals exposed to PTU were treated with pure standard drug thyroxine at a dose of 10 μg/kg of body weight by oral route and the test drug betulinic acid 20 mg/kg by oral route through force feeding in their respective groups. Treatment was carried out for a period of 2 months. Group with PTU-induced hypothyroidism showed an elevation in serum TSH and reduction level, which was restored by the betulinic acid in treated female albino rats. Betulinic acid also reduced the damage caused in the thyroid tissues by PTU, thus minimizing the symptoms of hypothyroidism. Histopathological examinations of the thyroid tissue showed changes in the thyrocytes of PTU-treated group while thyroxine group showed normal thyroid follicles cell architecture and the group treated with betulinic acid also showed marked improvement in the follicles integrity which shows that betulinic acid has some protective activity. This study shows that the betulinic acid has thyroid-enhancing potential by lowering down the TSH levels and reducing the damage caused in the thyroid tissues, thus minimizing the symptoms of hypothyroidism when used anaphylactically in rats.     

Hypothyroid myopathy with unusually high serum creatine kinase values

Depending on the degree of hormone deficiency, skeletal muscle involvement may occur in hypothyroidism. Usually, hypothyroid myopathy is associated with creatine kinase values <5,000 U/l. We report a 54-year-old man suffering from increasing fatigability, hoarseness, gait disturbances and a creatine kinase of 9,000 (normal: <80 U/l). He presented with bradyphrenia, macroglossia, dysarthria, myxedema, monoparesis, reduced deep tendon reflexes and stocking-type sensory disturbances. Free triiodthyronine was 0.25 pg/ml (normal: 0.6-1.9 pg/ml), free thyroxine <0.1 ng/dl (normal: 0. 6-1.8 ng/dl) and the thyroid-stimulating hormone >48.0 (normal: 0. 1-4.0 IU). Clinical neurologic examination and electromyography were compatible with myopathy and polyneuropathy. Other causes of myopathy, except hypothyroidism, were excluded. After L-thyroxine therapy (1.7 microg/kg BW/day) during 3 months, the patient's symptoms and signs vanished, except for sensory disturbances, and creatine kinase values and electromyography became normal. Severe hypothyroidism may be associated with highly elevated creatine kinase and myopathy. Adequate therapy leads to complete recovery, including myopathy.     

Blocking activity to action of thyroid stimulating hormone in serum from patients with primary hypothyroidism.

Spontaneous primary hypothyroidism in adults is usually associated with autoimmune thyroiditis. The hypothesis that hypothyroidism may result from the presence in serum of a factor that blocks stimulation of the thyroid by thyroid stimulating hormone was examined. Serum samples were collected from 28 patients with recently diagnosed primary hypothyroidism. After removal of endogenous thyroid stimulating hormone the effect of the serum on secretion of triiodothyronine induced by thyroid stimulating hormone or thyroid stimulating antibodies was examined in thyroid slices incubated in vitro. Serum samples from six of the patients demonstrated significant blocking of the stimulation by bovine thyroid stimulating hormone. Inhibition of the stimulatory action of thyroid stimulating antibodies was also exhibited by serum samples with blocking activity. It is concluded that in some patients with primary hypothyroidism a serum factor, which is probably an IgG, exists that can block the thyroid response to thyroid stimulating hormone and thyroid stimulating antibodies; it may represent an important mechanism in the pathogenesis of hypothyroidism.     

Enhancement of recombinant human EPO production and sialylation in chinese hamster ovary cells through Bombyx mori 30Kc19 gene expression

Productivity and sialylation are two important factors for the production of recombinant glycoproteins in mammalian cell culture. In our previous study, we found that silkworm hemolymph increased the sialylation of recombinant secreted human placental alkaline phosphatase in the insect cells, promoted the transfer of sialic acids onto the glycoprotein oligosaccharides in an in vitro asialofetuin sialylation system, and enhanced recombinant protein production in the Chinese hamster ovary (CHO) cells. These beneficial effects were mainly due to the 30K proteins, which consist of five isoforms. Among the 30K proteins, 30Kc19 was determined to be the major component. In this study, the 30Kc19 gene was introduced into a CHO cell line producing recombinant human erythropoietin, and its effects on productivity and sialylation were investigated. The transient expression of 30Kc19 significantly improved the production and sialylation of EPO. A stable cell line containing 30Kc19 was also established to investigate the effect of 30Kc19 gene expression. The stable expression of 30Kc19 increased the production and sialylation by 102.6% and 87.1%, respectively. The enhanced productivity from 30Kc19 expression is believed to occur because the 30Kc19 protein suppresses the loss of mitochondrial membrane potential and consequently improves the generation of intracellular ATP. In addition, the positive effect of 30Kc19 expression on sialylation is believed to be due to its ability to maintain sialyltransferase activity. In conclusion, 30Kc19 expression is a novel approach to improve the production and sialylation of recombinant glycoproteins in CHO cells.     

Unchanged Serum Adipokine Concentrations in the Setting of Short-Term Thyroidectomy-Induced Hypothyroidism

ObjectiveTo investigate short-term effects of thyroidectomy-induced hypothyroidism on leptin, adiponectin, and resistin concentrations in association with anthropometric data.MethodsThirty premenopausal women with euthyroid nodulargoiter-mean age, 44.0 ± 11.6 years; mean body mass index (BMI), 28.6 ± 5.9 kg/m²; 13 obese, 7 overweight, and 10 normal weight subjects—scheduled for total thyroidectomy were included in the study. Serum leptin, adiponectin, resistin, free triiodothyronine, free thyroxine, thyroid-stimulating hormone, glucose, insulin, and C-reactive protein concentrations, lipid profile, and anthropometric variables were determined in the euthyroid state (preoperatively) and the hypothyroid state (postoper atively, with a thyroid-stimulating hormone concentration > 30 mIU/L).ResultsBody weight, BMI, waist and hip circumferences, body fat mass, and serum lipid concentrations increased significantly after thyroidectomy. No significant difference was found between preoperative and postoperative serum leptin, adiponectin, and resistincon centrations. Fat tissue mass-corrected leptin, adiponectin, and resistin concentrations did not differ significantly between euthyroid and hypothyroid periods. Thyroid hor mone concentrations showed no significant correlations with adipokine levels.ConclusionSerum adipokine concentrations seem not to change significantly during short-term thyroidec tomy-induced hypothyroidism despite significant increases in body weight, BMI, fat mass, and lipid concentrations.(Endocr Pract. 2012;18:887-893)     

Sulfation of the tumor cell surface sialomucin of the 13762 rat mammary adenocarcinoma

ASGP-1, the major cell surface sialomucin of the 13762 ascites rat mammary adenocarcinoma, is at least 0.5% of the total ascites cell protein and has sulfate on 20% of its O-linked oligosaccharide chains. We have used this system to investigate the O-glycosylation pathway in these cells and to determine the temporal relationship between sulfation and sialylation. The two major sulfated oligosaccharides (S-1 and S-2) were isolated as their oligosaccharitols by alkaline borohydride elimination, anion exchange HPLC, and ion-suppression HPLC. From structural analyses S-1 is proposed to be a branched, sulfated trisaccharide -O4S-GlcNAc beta 1,6-(Gal beta 1,3)-GalNAc and S-2 its sialylated derivative -O4S-GlcNAc beta 1,6-(NeuAc alpha 2,3-Gal beta 1,3)-GalNac. Pulse labeling with sulfate indicated that sulfation occurred primarily on a form of ASGP-1 intermediate in size between immature and mature sialomucin. Pulse-chase analyses showed that the intermediate could be chased into mature ASGP-1. The concomitant conversion of S-1 into S-2 had a half-time of less than 5 min. Monensin treatment of the tumor cells led to a 95% inhibition of sulfation with the accumulation of unsulfated trisaccharide GlcNAc beta 1,6-(Gal beta 1,3)-GalNAc and sialylated derivative GlcNAc beta 1,6-(NeuAc alpha 2,3-Gal beta 1,3)-GalNAc. These data suggest that sulfation of ASGP-1 is an intermediate synthetic step, which competes with beta-1,4-galactosylation for the trisaccharide intermediate and thus occurs in the same compartment as beta-1,4-galactosylation. Moreover, sulfation precedes sialylation, but the two are rapidly successive kinetic events in the oligosaccharide assembly of ASGP-1.     

Are We Restoring Thyroid Hormone Signaling in Levothyroxine-Treated Patients With Residual Symptoms of Hypothyroidism?

IntroductionLevothyroxine (LT4) at doses that maintain the serum thyroid-stimulating hormone levels within the normal range constitutes the standard of care for the treatment of hypothyroidism. After a few months, this eliminates the signs and symptoms of overt hypothyroidism in the majority of patients, owing to the endogenous activation of thyroxine to triiodothyronine, the biologically active thyroid hormone. Still, a small percentage of the patients (10%-20%) exhibit residual symptoms, despite having normal serum thyroid-stimulating hormone levels. These symptoms include cognitive, mood, and metabolic deficits, with a significant impairment in psychological well-being and quality of life.ObjectiveTo provide a summary of progress in the approach of patients with hypothyroidism that exhibit residual symptoms despite treatment.MethodsWe reviewed the current literature and here we focused on the mechanisms leading to a deficiency of T3 in some LT4-treated patients, the role of residual thyroid tissue and the rationale for combination therapy with LT4 + liothyronine (LT3).ResultsA score of clinical trials comparing therapy with LT4 versus LT4 + LT3 concluded that both are safe and equally effective (neither is superior); however, these trials failed to recruit a sufficiently large number of patients with residual symptoms. New clinical trials that considered LT4-treated symptomatic patients revealed that such patients benefit from and prefer therapy containing LT4 + LT3; desiccated thyroid extract has also been used with similar results. A practical approach to patients with residual symptoms and on initiation of combination therapy with LT4 + LT3 is provided.ConclusionA recent joint statement of the American, British, and European Thyroid Associations recommends that a trial with combination therapy be offered to patients with hypothyroidism that do not fully benefit from therapy with LT4.