Weight Loss Through Gastric Banding: Effects on TSH and Thyroid Hormones in Obese Subjects With Normal Thyroid Function

Studies on thyroid function in obesity yielded inconsistent results; high thyroid‐stimulating hormone (TSH) levels were generally shown; high free triiodothyronine (fT)‐3 or fT4 levels were described in some, but not in other studies. After weight loss, TSH and thyroid hormones have been described to either increase or decrease. Our aim was to describe TSH, fT3, and fT4 in obese subjects with normal thyroid function before and after durable and significant weight loss, obtained through laparoscopic gastric banding (LAGB), in comparison with nonobese subjects. TSH, fT3, fT4, and fT3/fT4 ratio (an index of D1 and D2 deiodinase activity), were evaluated in 99 healthy controls and in 258 obese subjects, at baseline and 6 months, 1 year, and 2 years after LAGB, together with indexes of glucose (glucose, insulin, homeostasis model assessment of insulin resistance index) and lipid (triglycerides, total and high‐density lipoprotein–cholesterol) metabolism, and anthropometric measures (BMI and waist circumference). Under basal conditions, TSH, fT3, and fT4 were all in the normal range, but higher in obese than in nonobese subjects, and fT3/fT4 ratio was normal; with weight loss, fT3 and fT3/fT4 ratio decreased in obese subjects, while fT4 increased and TSH remained steady; all values were again within the normal range. Albumin and cholesterol levels remained steady, while triglycerides, insulin, and homeostasis model assessment of insulin resistance decreased, and high‐density lipoprotein–cholesterol increased. These changes, however, do not modify TSH, letting us to hypothesize that the changes are due to a decrease of D1 and D2 deiodinase activities.     

Thyroid Functions and Trace Elements in Pediatric Patients with Exogenous Obesity

Obesity is a multifactorial disease developing following impairment of the energy balance. The endocrine system is known to be affected by the condition. Serum thyroid hormones and trace element levels have been shown to be affected in obese children. Changes in serum thyroid hormones may result from alterations occurring in serum trace element levels. The aim of this study was to evaluate whether or not changes in serum thyroid hormone levels in children with exogenous obesity are associated with changes in trace element levels. Eighty-five children diagnosed with exogenous obesity constituted the study group, and 24 age- and sex-matched healthy children made up the control group. Serum thyroid stimulating hormone (TSH), free thyroxine (fT4), free triiodothyronine (fT3), thyroglobulin (TG), selenium (Se), zinc (Zn), copper (Cu), and manganese (Mn) levels in the study group were measured before and at the third and sixth months of treatment, and once only in the control group. Pretreatment fT4 levels in the study group rose significantly by the sixth month (p?=?0.006). Zn levels in the patient group were significantly low compared to the control group (p?=?0.009). Mn and Se levels in the obese children before and at the third and sixth months of treatment were significantly higher than those of the control group (p?=?0.001, p?=?0.001). In conclusion, fT4, Zn, Cu, Mn, and Se levels are significantly affected in children diagnosed with exogenous obesity. The change in serum fT4 levels is not associated with changes in trace element concentrations.     

Thyroid function, cytokine and IGF-IGFBP interactions in cystic fibrosis patients

BACKGROUND/AIMS: Thyroid function impairment has been sporadically described in cystic fibrosis (CF) and ascribed to iodine overload or selenite deficiency. In this study we evaluated thyroid function in CF in order to verify these data and to evaluate if the modifications were related to serum levels of markers of inflammation and growth factors that we have previously shown to be altered in CF. METHODS: Seventeen young adult CF patients and 18 age-matched controls were enrolled in this study. The diagnosis of CF was confirmed by genetic analysis. None was treated with pulmonary expectorants. Serum IL-1beta, IL-6, TNF-alpha, IGF-I, IGF-II, IGFBP-2, IGFBP-3, TSH, fT3 and fT4 were measured using standard commercial kits. RESULTS: TSH, fT3 and fT4 serum levels were similar in CF patients and controls. Within the patient group, thyroid function did not vary in relation to C-reactive protein serum levels, respiratory function and clinical conditions (Shwachman score). No correlation was found with any growth factor or cytokine analyzed. CONCLUSIONS: At variance with the few previously published data, we did not detect any difference in thyroid function in patients with CF compared with normal healthy subjects. This could be due to the fact that no iodine overload or selenite deficiency was present in our patients. Thyroid function seemed independent of markers of inflammation and IGF-IGFBP serum levels.     

Thyroid function derangement and childhood obesity: an Italian experience

Background

In recent years, there has been an increasing attention to thyroid function in paediatric obese patients. In the present study we aimed 1) to determine the prevalence of abnormally elevated thyroid-stimulating hormone (TSH) levels in Italian obese children and adolescents 2) to investigate whether hyperthyrotropinemia in obese children cardiovascular and metabolic risk factors 3) to verify if TSH elevation is reversible after weight loss.

Methods

We examined 938 obese children and adolescents (450 females). Anthropometric, metabolic and hormonal variables were determined at baseline and, in a subgroup of children with hyperthyrotropinemia, after a six month weight loss program.

Results

Hyperthyrotropinemia (TSH ≥4.2 μUI/ml) was diagnosed in 120 patients (12,8%). Body mass index (BMI) z-score (p = 0.02) and free T3 (fT3) levels (p = 0.03) were higher in patients with elevated TSH compared to the group with normal TSH. There were not significant differences in other metabolic parameters between the two groups. A positive correlation between baseline TSH and BMI z-score (p = 0.0045) and between Ft3 and BMI z-score (p = 0.0034) was observed, while there was no correlation between TSH and lipids. Twenty-three patients among those with hyperthyrotropinemia who participated to weight reduction intervention (64 patients), presented substantial weight loss and concomitantly a significant decrease in TSH and in fT3.

Conclusions

These results suggest that: (1) a moderate elevation of TSH concentrations, is frequently found in obese children; (2) in obese children increase of TSH is not associated to metabolic risk factors, (3) hyperthyrotropinemia is reversible after weight loss and these data suggest that it should not be treated.     

Visualizing density maps with UCSF Chimera

We describe methods for interactive visualization and analysis of density maps available in the UCSF Chimera molecular modeling package. The methods enable segmentation, fitting, coarse modeling, measuring and coloring of density maps for elucidating structures of large molecular assemblies such as virus particles, ribosomes, microtubules, and chromosomes. The methods are suitable for density maps with resolutions in the range spanned by electron microscope single particle reconstructions and tomography. All of the tools described are simple, robust and interactive, involving computations taking only seconds. An advantage of the UCSF Chimera package is its integration of a large collection of interactive methods. Interactive tools are sufficient for performing simple analyses and also serve to prepare input for and examine results from more complex, specialized, and algorithmic non-interactive analysis software. While both interactive and non-interactive analyses are useful, we discuss only interactive methods here.     

Cardiovascular autonomic function tests in an African population

Background

Age- and sex-specific reference intervals are an important prerequisite for interpreting thyroid hormone measurements in children. However, only few studies have reported age- and sex-specific pediatric reference values for TSH_basal (TSH), free T3 (fT3), and free T4 (fT4) so far. Reference intervals are known to be method- and population-dependent. The aim of our study was to establish reference intervals for serum TSH, fT3, and fT4 from birth to 18 years and to assess sex differences.

Methods

2,194 thyroid hormone tests obtained from a hospital-based pediatric population were included into our retrospective analysis. Individuals with diagnoses or medications likely to affect thyroid function were primarily excluded, as well as the diagnostic groups, if different from the purely healthy subgroup (n = 414). Age groups were ranging from 1 day to 1 month, 1 – 12 months, and 1 – 5, 6 – 10, 11 – 14, and 15 – 18 years, respectively. Levels of fT3, fT4 and TSH were measured on Advia^® Centaur? automated immunoassay system.

Results

The final sample size for reference data creation was 1,209 for TSH, 1,395 for fT3, and 1,229 for fT4. Median and 2.5/10/25/75/90/97.5 percentiles were calculated for each age group. Males had greater mean fT3 concentrations than females (p < 0.001). No sex-differences were found for TSH and fT4 between age-matched serum samples. Median concentrations of fT3, fT4 and TSH were greatest during the first month of life, followed by a continuous decline with age.

Conclusion

Our results corroborate those of previous studies showing that thyroid hormone levels change markedly during childhood, and that adult reference intervals are not universally applicable to children. Moreover, differences of our reference intervals compared to previous studies were observed, likely caused by different antibody characteristics of various analytical methods, different populations or undefined geographic covariates, e.g. iodine and selenium status.     

Iodine in autism spectrum disorders

ObjectiveThe aim of our study was to assess the iodine status of Polish boys with severe autism compared to their healthy peers and evaluate the relationship between urinary iodine, thyroid hormones, body mass index and Autism Spectrum Disorder (ASD) symptomatology.Subjects and methodsTests were performed in 40 boys with ASD and 40 healthy boys, aged 2–17 from the same geographic region in Poland. Urinary iodine (UI), free triiodothyronine (fT3), free thyroxine (fT4), thyroid stimulating hormone (TSH), BMI, and individual symptoms measured by the Childhood Autism Rating Scale (CARS) were correlated.Validated ion chromatography method with pulsed amperometric detection was applied for the determination of urinary iodine after optimized alkaline digestion in a closed system assisted with microwaves.Results19 out of 40 children with ASD had mild to moderate iodine deficiency. Statistically significant lower levels of UI, fT3 and fT4 and higher levels of TSH were found in the autistic group when compared with the control group. Concentration of iodine in urine was negatively associated with clinician’s general impression for children between 11 and 17 years. Emotional response, adaptation to environmental change, near receptor responsiveness, verbal communication, activity level, and intellectual functioning are more associated with UI than other symptoms listed in CARS.ConclusionThe severity of certain symptoms in autism is associated with iodine status in maturing boys. Thyroid hormones were within normal reference ranges in both groups while urinary iodine was significantly lower in autistic boys suggesting that further studies into the nonhormonal role of iodine in autism are required.     

The Relation Between Human Exposure to Mercury and Thyroid Hormone Status

The aim of this study was to investigate total mercury (THg) and methylmercury (MeHg) exposure of 75 mother-child pairs in relation to their thyroid hormone status (thyroid-stimulating hormone (TSH), triiodothyronine (T3), free triiodothyronine (fT3), thyroxine (T4), and free thyroxine (fT4)). THg and MeHg in blood samples were measured by atomic absorption spectrometry and gas chromatography-inductively coupled plasma-mass spectrometry, respectively. The median THg and MeHg levels in maternal blood, cord blood, and blood of 6-month-old children were 0.50, 0.53, and 0.32 and 0.22, 0.32, and 0.08 μg/L, respectively. There were significant correlations between paired maternal-cord blood levels for THg and MeHg, with a greater transplacental transport of MeHg compared with THg (mean cord/maternal blood ratio, 1.80 vs. 1.24). The maternal blood THg was found to be a better predictor of TSH levels in children than their current THg exposure. There was a positive correlation between maternal THg and children's TSH. T3 and fT3 levels in children were negatively related to cord blood THg in the majority (Caucasian) subgroup, whereas these associations were positive in the Roma subgroup. Mothers with dental amalgam fillings had significantly lower T4 and fT4 levels. Moreover, fT4 in the mothers of boys negatively correlated with maternal THg levels. MeHg exposure lowered T3 levels in the mothers of girls. Our results suggest that low-level exposure to Hg can affect thyroid hormone status during prenatal and early postnatal exposure depending on the form of Hg, gender, ethnicity, lifestyle, or socioeconomic status (dental amalgam fillings).     

Compensatory role of thyroid hormone receptor (TR) alpha 1 in resistance to thyroid hormone: study in mice with a targeted mutation in the TR beta gene and deficient in TR alpha 1

Resistance to thyroid hormone (RTH) is caused by mutations of the thyroid hormone receptor beta (TR beta) gene. Almost all RTH patients are heterozygous with an autosomal dominant pattern of inheritance. That most are clinically euthyroid suggests a compensatory role of the TR alpha1 isoform in maintaining the normal functions of thyroid hormone (T3) in these patients. To understand the role of TR alpha1 in the manifestation of RTH, we compared the phenotypes of mice with a targeted dominantly negative mutant TR beta (TR betaPV) with or without TR alpha1. TR betaPV mice faithfully recapitulate RTH in humans in that these mice demonstrate abnormalities in the pituitary-thyroid axis and impairment in growth. Here we show that the dysregulation of the pituitary-thyroid axis was worsened by the lack of TR alpha1 in TR betaPV mice, and severe impairment of postnatal growth was manifested in TR betaPV mice deficient in TR alpha1. Furthermore, abnormal expression patterns of T3-target genes in TR betaPV mice were altered by the lack of TR alpha1. These results demonstrate that the lack of TR alpha1 exacerbates the manifestation of RTH in TR betaPV mice. Therefore, TR alpha1 could play a compensatory role in mediating the functions of T3 in heterozygous patients with RTH. This compensatory role may be especially crucial for postnatal growth.     

Thyroid dysfunction in obese pre-pubertal children: oxidative stress as a potential pathogenetic mechanism

Although a relationship between obesity and hyperthyrotropinemia has been hypothesized in obese children, the underlying pathogenesis is not completely known. In the current cross-sectional study, we evaluated the thyroid function in a group of 80 obese pre-pubertal children compared to 41 healthy normal weight peers, exploring the possible association between hyperthyrotropinemia and oxidative stress. In all children, thyrotropin (TSH), free T4 (fT4), free T3 (fT3) and anti-thyroid antibodies were evaluated. Homeostatic model assessment of insulin resistance (HOMA-IR) level was evaluated as index of insulin resistance. We measured the endogenous secretory receptor for advanced glycation end products (esRAGE) and soluble RAGE (sRAGE) and the urinary prostaglandin F2α (PGF-2α) as markers of oxidative stress. We found that TSH levels were significantly higher in obese children than controls. TSH significantly correlated with body mass index-standard deviation score (BMI-SDS), HOMA-IR, PGF-2α, esRAGE and sRAGE. The multiple linear regression showed that in obese children HOMA-IR, PGF-2α, esRAGE and sRAGE were significantly related to TSH, independently of BMI-SDS, age and gender. In obese children, hyperthyrotropinemia could be detected already in pre-pubertal age. The increased oxidative stress might represent one of the key regulators of TSH levels, early in life.     

Circannual rhythm of plasma thyrotropin in middle-aged and old euthyroid subjects

The circannual rhythm of plasma thyrotropin (TSH) was evaluated in 8,310 euthyroid, serially independent, young, middle-aged and old men and women. A statistically significant circannual rhythm of plasma TSH was validated, by the mean group-cosinor method, in the middle-aged and old men and women (p less than 0.05), with acrophase in December, whereas the young subjects did not show any rhythm. No significant correlation was found between TSH plasma levels and free thyroxine (fT4) or ambient temperature in any group. Moreover, plasma fT4 did not show seasonal variations.     

MMB-GUI: a fast morphing method demonstrates a possible ribosomal tRNA translocation trajectory

Easy-to-use macromolecular viewers, such as UCSF Chimera, are a standard tool in structural biology. They allow rendering and performing geometric operations on large complexes, such as viruses and ribosomes. Dynamical simulation codes enable modeling of conformational changes, but may require considerable time and many CPUs. There is an unmet demand from structural and molecular biologists for software in the middle ground, which would allow visualization combined with quick and interactive modeling of conformational changes, even of large complexes. This motivates MMB-GUI. MMB uses an internal-coordinate, multiscale approach, yielding as much as a 2000-fold speedup over conventional simulation methods. We use Chimera as an interactive graphical interface to control MMB. We show how this can be used for morphing of macromolecules that can be heterogeneous in biopolymer type, sequence, and chain count, accurately recapitulating structural intermediates. We use MMB-GUI to create a possible trajectory of EF-G mediated gate-passing translocation in the ribosome, with all-atom structures. This shows that the GUI makes modeling of large macromolecules accessible to a wide audience. The morph highlights similarities in tRNA conformational changes as tRNA translocates from A to P and from P to E sites and suggests that tRNA flexibility is critical for translocation completion.     

Dual functions of the steroid hormone receptor coactivator 3 in modulating resistance to thyroid hormone

Mutations of the thyroid hormone receptor beta (TRbeta) gene cause resistance to thyroid hormone (RTH). RTH is characterized by increased serum thyroid hormone associated with nonsuppressible thyroid-stimulating hormone (TSH) and impaired growth. It is unclear how the actions of TRbeta mutants are modulated in vivo to affect the manifestation of RTH. Using a mouse model of RTH that harbors a knockin mutation of the TRbeta gene (TRbetaPV mouse), we investigated the effect of the steroid hormone receptor coactivator 3 (SRC-3) on RTH. In TRbetaPV mice deficient in SRC-3, dysfunction of the pituitary-thyroid axis and hypercholesterolemia was lessened, but growth impairment of RTH was worsened. The lessened dysfunction of the pituitary-thyroid axis was attributed to a significant decrease in growth of the thyroid and pituitary. Serum insulin-like growth factor 1 (IGF-1) was further reduced in TRbetaPV mice deficient in SRC-3. This effect led to reduced signaling of the IGF-1/phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway that is known to mediate cell growth and proliferation. Thus, SRC-3 modulates RTH by at least two mechanisms, one via its role as a receptor coregulator and the other via its growth regulatory role through the IGF-1/PI3K/AKT/mTOR signaling.     

Nucleic acid visualization with UCSF Chimera

With the increase in the number of large, 3D, high-resolution nucleic acid structures, particularly of the 30S and 50S ribosomal subunits and the intact bacterial ribosome, advancements in the visualization of nucleic acid structural features are essential. Large molecular structures are complicated and detailed, and one goal of visualization software is to allow the user to simplify the display of some features and accent others. We describe an extension to the UCSF Chimera molecular visualization system for the purpose of displaying and highlighting nucleic acid characteristics, including a new representation of sugar pucker, several options for abstraction of base geometries that emphasize stacking and base pairing, and an adaptation of the ribbon backbone to accommodate the nucleic acid backbone. Molecules are displayed and manipulated interactively, allowing the user to change the representations as desired for small molecules, proteins and nucleic acids. This software is available as part of the UCSF Chimera molecular visualization system and thus is integrated with a suite of existing tools for molecular graphics.     

Maternal thyroid hormone trajectories during pregnancy and child behavioral problems

There is ample evidence demonstrating the importance of maternal thyroid hormones, assessed at single trimesters in pregnancy, for child cognition. Less is known, however, about the course of maternal thyroid hormone concentrations during pregnancy in relation to child behavioral development. Child sex might be an important moderator, because there are sex differences in externalizing and internalizing behavioral problems. The current study examined the associations between maternal thyroid hormone trajectories versus thyroid assessments at separate trimesters of pregnancy and child behavioral problems, as well as sex differences in these associations. In 442 pregnant mothers, serum levels of TSH and free T4 (fT4) were measured at 12, 24, and 36 weeks gestation. Both mothers and fathers reported on their children's behavioral problems, between 23 and 60 months of age. Latent growth mixture modeling was used to determine the number of different thyroid hormone trajectories. Three trajectory groups were discerned: 1) highest and non-increasing TSH with lowest fT4 that decreased least of the three trajectories; 2) increasing TSH and decreasing fT4 at intermediate levels; 3) lowest and increasing TSH with highest and decreasing fT4. Children of mothers with the most flattened thyroid hormone trajectories (trajectory 1) showed the most anxiety/depression symptoms. The following trimester-specific associations were found: 1) lower first-trimester fT4 was associated with more child anxiety/depression, 2) higher first-trimester TSH levels were related to more attention problems in boys only. A flattened course of maternal thyroid hormone concentrations during pregnancy was a better predictor of child anxiety/depression than first-trimester fT4 levels.     

The Interaction Between Selenium Status, Sex Hormones, and Thyroid Metabolism in Adolescent Girls in the Luteal Phase of their Menstrual Cycle

The objective of the present work was to study all physiological relationships among selenium status (SeS), sex hormones secretion (SH), and thyroid metabolism (ThM) in healthy adolescent girls, at one time. Forty-four girls aged 13.4–16.6 years (mean age, 14.5 ± 0.5 years) entered the statistical model. Parameters reflecting SeS: plasma selenium concentration (Se) and plasma glutathione peroxidase activity (GPX3); SH: serum estradiol (E₂) and progesterone (P₄); age of menarche (AoM); and ThM: thyroid stimulating hormone (TSH), free thyroxine (fT4), free triiodothyronine (fT3), antithyroid peroxidase antibodies (anti-TPO) in serum, and thyroid volume (ThV), were determined, and the interactions between them were evaluated by means of the partial least squares method (PLS). PLS method was, for the first time, successfully applied to the problem of selenium and hormone interactions and revealed that selenium status and female reproductive system are interrelated and affect thyroid physiology in adolescent girls in the luteal phase. The strongest associations were revealed for the pairs of parameters, Se and fT4/fT3, Se and P₄, the modest ones for the pairs, Se and ThV, P₄ and fT4/fT3, Se and AoM, and P₄ and AoM. There was no correlation between E₂, GPX3, and TSH, and any other considered parameter. Se and P₄ had the greatest influence on ThM parameters.     

A novel thyroid hormone receptor-beta mutation,not anticipated to occur in resistance to thyroid hormone,causes variable phenotypes

Resistance to thyroid hormones (RTH) is a syndrome characterized by a variable tissue hyposensitivity to thyroid hormones and is linked to mutations in the thyroid hormone receptor-beta (TRbeta) gene. We report here for the first time in vivo the mutation R429W (CCG-->TCG) located in the exon 10. The artificial mutant obtained in vitro displayed a normal T(3)-binding affinity and transactivation function. Therefore, it was thought to produce little, if any, clinical effect and to escape to clinical detection. The present report is at least in part discordant with this prediction since the propositus and his grandmother had an authentic hyperthyroidism with high FT(4) plasma level in the presence of inappropriate TSH. On the other hand, spontaneous variations of clinical features and - interestingly - of plasma FT(4) concentrations with time in the propositus, and the phenotype observed in his mother who never complained with thyrotoxic symptoms, confirmed the in vitro binding and functional predictions. The most intriguing is the clinical course of the grandmother as she first presented with predominant pituitary RTH and a diffuse goiter and finally with a toxic multinodular goiter with normal T(3) and T(4) plasma concentrations and suppressed TSH. In conclusion, we report a novel mutation in the gene encoding the thyroid hormone receptor responsible for predominant pituitary RTH already described in vitro but not in vivo. The fluctuant phenotype of the propositus suggests that other factors modulate the degree of tissue resistance that is under genetic control. Toxic multinodular goiter, possibly due to chronic TSH stimulation during RTH, in addition to the phenotype variability, increases the difficulty to diagnose this thyroid disorder.     

Thyroid and hypoxic stress in the newt Triturus carnifex

When specimens of the newt Triturus carnifex, under anaesthesia by submersion in a 0.2% chlorbutol solution for 25 min, are isolated in a respiratory chamber at 18 degrees C containing water with only 1.3 ppm of oxygen, they consume the oxygen completely in about 3 hr, but they can stay alive for many more hours and wake up with no apparent exterior consequences. Hypoxia induces rapid onset of hepatic steatosis and melanosis, as well as a controlled haemolytic process involving a pool of red blood cells of the same order of size as that held as a reserve in the spleen by animals in an aerial habitat. At the origin of the phenomena is an intense response by the hypophysis, histologically detectable 1 hr from the onset of treatment and confirmed 2 hr later by a highly significant increase in the plasma thyroidstimulating hormone (TSH) concentration compared with the controls (41.5 +/- 13.7 microU/L vs. 15.5 +/- 6.2; P < 0.005). The thyroid follicles react by reabsorbing their colloid, but instead of an increase in the plasma free T3 and T4 concentrations, fT3 falls significantly (1.5 +/- 0.3 pg/mL vs., the 2.4 +/- 0.7; P < 0.05), whereas fT4 remains stationary (4.0 +/- 0.5 pg/mL vs. 4.6 +/- 0.8; N.S.). After 6 hr, the plasmatic TSH concentration is still higher than in the controls (27.0 +/- 3.0 microU/L vs. 15.5 +/- 6.2; P < 0.05), whereas fT3 and fT4 remain stable (1.5 +/- 0.3 and 4.4 +/- 0.5 pg/mL, respectively). If T3 or T4 labelled with 125I is administered prior to hypoxia, after 6 hr of treatment the radioactivity is found to be limited exclusively to the liver and kidney; the thyroid, gall bladder and gut result negative, and this does not agree with hypotheses of hormone inactivation by deiodination, sulphation or glucuronidation. This apparently peculiar endocrine path has not been observed in previous studies on hypoxia in vertebrates, because the experiments were always designed to analyse plasma hormone levels after at least 24 hr of hypoxia or during chronic treatments, losing the most interesting phases of the endocrine response. The possibility that the hypoxic newt possesses alternative or complementary metabolic pathways to anaerobic glycolysis to sustain steatogenesis and melanogenesis and maintain the same cardiac activity as the controls is briefly discussed.     

Oxytocin decreases plasma levels of thyroid-stimulating hormone and thyroid hormones in rats

Oxytocin (OXT) administered to rats induces several long-lasting physiological and metabolic effects. The aim of the present study was to investigate the effects of oxytocin treatment on plasma levels of thyroid-stimulating hormone (TSH), free thyroxine (fT4) and free triiodothyronine (fT3). For this purpose, oxytocin or NaCl was administered intracerebroventricularly (i.c.v.) (0.3 micro g) or subcutaneously (s.c.) (1 mg/kg) once a day for 5 days to male rats. Five or ten days after the last injection, rats were decapitated, blood was collected and hormone levels were analyzed by fluoroimmunoassay. The oxytocin treatment i.c.v. decreased plasma levels of TSH (p<0.05), fT3 (p<0.01) and fT4 (p<0.05) when measured at day 5 after oxytocin treatment, whereas the effect was abolished when measured at day 10. Oxytocin treatment s.c. did not affect plasma levels of TSH, fT3 or fT4. Thus, the effect seems to have been mediated within the central nervous system, and TSH and the thyroid hormones may be involved in some of the metabolic effects in response to oxytocin.