Increased hepatobiliary clearance of unconjugated thyroxine determines DMP 904-induced alterations in thyroid hormone homeostasis in rats.

4-(3-pentylamino)-2,7-dimethyl-8-(2-methyl-4-methoxyphenyl)-pyrazolo-[1,5-a]-pyrimidine (DMP 904) is a potent and selective antagonist of corticotropin releasing factor receptor-1 (CRF1 receptor) with an efficacious anxiolytic profile in preclinical animal models. In subchronic toxicity studies in Sprague-Dawley rats, DMP 904 produced thyroid follicular cell hypertrophy and hyperplasia, and a low incidence of follicular cell adenoma. The current investigations were designed to determine the mode of action by which DMP 904 disrupts thyroid homeostasis in male rats. Five-day treatment with DMP 904 (300 mg/kg/day) dramatically lowered serum thyroxine (T4) to levels below detectable limits (< 1 microg/dl) by 72 h, with concurrent decreases in triiodothyronine (T3, about a 70% decrease) and increases in thyroid stimulating hormone (TSH; about a three-fold increase). DMP 904 increased [125I]T4 total body clearance (Cl tb) (38.21 +/- 10.45 ml/h) compared to control (5.61 +/- 0.59 ml/h) and phenobarbital-treated rats (7.92 +/- 1.62 ml/h). This increase in Cl(tb) was associated with a significant increase in biliary clearance (Cl bile) of unconjugated [125I]T4 (nearly 80-times control rates) and increased liver:blood ratios of T4, suggestive of enhanced hepatic uptake of T4. A single dose of DMP 904 (200 mg/kg) increased mRNA levels of hepatic cytochrome P450s (CYP 3A1 and CYP 2B1) and UDP-glucuronosyltransferases (UGT 1A1 and UGT 1A2). DMP 904 also induced mRNAs of the canalicular transporter, multi-drug resistance protein-2 (Mrp2) and sinusoidal transporters, organic anion transporting proteins (Oatp1 and Oatp2) within 24 h. Western blot analysis confirmed DMP 904 related increases in Oatp2 protein expression. Collectively, these data suggest that DMP 904 is an agonist of the constitutive androstane receptor (CAR) and pregnane X receptor (PXR) and that the decreased serum levels of T4 and T3 resulted from increased hepatobiliary clearance. However, DMP 904 is distinguished from other compounds associated with similar effects on thyroid hormone homeostasis because its effects were primarily related to increased biliary excretion of unconjugated T4.     

Evaluation of hypothalamus‐pituitary‐thyroid axis function by chronic perchlorate exposure in male rats

Perchlorate is a widespread endocrine disruptor that was previously correlated with increased serum TSH levels and decreased thyroid hormones production both in animals and humans. Even so, the regulation of gene/protein expression in the hypothalamus, pituitary and thyroid by chronic perchlorate exposure was not completely elucidated. Therefore, this study aimed to investigate the underlying mechanisms involved in the disruption of hypothalamus‐pituitary‐thyroid axis by chronic perchlorate exposure. Male Wistar rats were treated or not with NaClO₄ in the drinking water (35 mg/Kg/day) for 60 days. Thereafter, hormone/cytokines serum levels were measured through multiplex assays; genes/proteins expression were investigated by qPCR/Western Blotting and thyroid morphology was evaluated through histological analysis. Serum TSH levels were increased and serum T₄/T₃ levels were decreased in perchlorate‐treated animals. This treatment also altered the thyrotropin‐releasing hormone mRNA/protein content in the hypothalamus. Additionally, the expression of both subunits of TSH were increased in the pituitary of perchlorate‐treated rats, which also presented significant alterations in the thyroid morphology/gene expression. Furthermore, perchlorate exposure reduced liver Dio1 mRNA expression and increased the content of pro‐inflammatory cytokines in the thyroid and the serum. In conclusion, our study adds novel findings about the perchlorate‐induced disruption of the hypothalamus‐pituitary‐thyroid axis gene/protein expression in male rats. The data presented herein also suggest that perchlorate induces thyroid and systemic inflammation through the increased production of cytokines. Taken together, our results suggest that perchlorate contamination should be monitored, especially in the individuals most susceptible to the deleterious effects of reduced levels of thyroid hormones.     

Depression, smoking abstinence and HPA function in women smokers

To determine whether smokers with a history of depression are differentially susceptible to smoking withdrawal, depressed mood induction and/or hypothalamic-pituitary-adrenal (HPA) axis dysregulation during smoking abstinence, 24 women smokers with and without such a history were studied. During one 5-day interval, participants smoked ad libitum; during a second they abstained. On day 4, the participants were exposed to the Velten mood induction procedure (VMIP). Participants were then instructed to take 1 mg dexamethasone at 11 pm. At 4 pm on day 5, blood samples were withdrawn to determine the cortisol and ACTH response. Despite lower baseline cotinine levels, history-positive participants displayed more pronounced overall withdrawal distress than did history-negative participants, regardless of condition. The VMIP increased depression as well as negative responses on other profile of mood states subscales. Despite many overall group differences, no significant main effects for smoking condition nor interaction effects emerged. All participants evinced cortisol suppression in response to dexamethasone during both conditions, but the degree of suppression did not differ as a function of either abstinence or depression history. In history-positive smokers, however, ACTH levels trended toward overall elevation and showed almost no suppression during abstinence; thus exacerbation of HPA dysregulation in history-positive smokers during smoking abstinence cannot be ruled out.     

Short circuit: Disaggregation of adrenocorticotropic hormone and cortisol levels in HIV‐positive,methamphetamine‐using men who have sex with men

Objective

This study examined if methamphetamine use alone (METH + HIV?) and methamphetamine use in combination with HIV (METH + HIV+) were associated with hypothalamic‐pituitary‐adrenal (HPA) axis dysregulation as well as insulin resistance relative to a nonmethamphetamine‐using, HIV‐negative comparison group (METH‐HIV?).

Methods

Using an intact groups design, serum levels of HPA axis hormones in 46 METH + HIV? and 127 METH + HIV+ men who have sex with men (MSM) were compared to 136 METH‐HIV? men.

Results

There were no group differences in prevailing adrenocorticotropic hormone (ACTH) or cortisol levels, but the association between ACTH and cortisol was moderated by METH + HIV+ group (β = ?0.19, p < .05). Compared to METH‐HIV? men, METH + HIV+ MSM displayed 10% higher log₁₀ cortisol levels per standard deviation lower ACTH. Both groups of methamphetamine‐using MSM had lower insulin resistance and greater syndemic burden (i.e., sleep disturbance, severe depression, childhood trauma, and polysubstance use disorder) compared to METH‐HIV? men. However, the disaggregated functional relationship between ACTH and cortisol in METH + HIV+ MSM was independent of these factors.

Conclusions

Further research is needed to characterize the bio‐behavioral pathways that explain dysregulated HPA axis functioning in HIV‐positive, methamphetamine‐using MSM.     

A preliminary study of dexamethasone treatment on pituitary–adrenal responsivity in major depression

Major depression is characterized by overactivity of the hypothalamic–pituitary–adrenal (HPA) axis. Dexamethasone (DEX), the glucocorticoid agonist, has been shown to be effective in the treatment of depression. We chose to examine the impact of a short course of DEX treatment on depressive symptomatology, and on the pituitary‐adrenal response to CRH administration. In this preliminary study, five subjects with major depression were treated for 4 days with 3 mg DEX; a CRH test was performed before and after treatment. Four subjects showed a reduction in ACTH (p=0·01) and cortisol output (p<0·01) following DEX treatment. All subjects showed a drop in depression scores after treatment; the Hamilton Depression score fell by 11·4±1·7 (mean±SEM) from baseline (p=0·01) and the Beck Depression score by 9·2±2·5 (mean±SEM) from baseline (p=0·01); this represented a reduction by almost 50 per cent from baseline levels on both depression indices. We suggest that the impact of DEX treatment on depressive symptoms may reflect a restraining influence on an overactive HPA, with a normalization of pituitary–adrenal response to CRH drive. Larger studies are required to investigate this further and to ascertain whether the mood and neuroendocrine changes induced by dexamethasone are sustained. Copyright © 1999 John Wiley & Sons, Ltd.     

Effect of acute hexavalent chromium exposure on pituitary–thyroid axis of a freshwater fish,Channa punctatus (Bloch)

Acute exposure to hexavalent chromium (10 mg L^?1, 20 mg L^?1, and 40 mg L^?1 potassium dichromate for 96 h) dose‐dependently affected the pituitary–thyroid axis of teleost, Channa punctatus. Significant hypertrophy of the thyroid follicle was observed in 20 mg L^?1 and 40 mg L^?1 groups; the follicular epithelium was however hypertrophied only in 40 mg L^?1 group. The colloid depletion in the lumen of thyroid follicle was evident in 20 mg L^?1 and 40 mg L^?1 groups. Serum thyroid hormones (thyroxine/T4 and triiodothyronine/T3) level increased significantly at both the higher doses. Increased immunointensity and significant hypertrophy of the pituitary thyrotrophs (anti TSHβ‐immunoreactive cells) was observed in both 20 mg L^?1 and 40 mg L^?1 chromium‐exposed fish. The increased thyroid hormones secretion observed in this study might be an adaptive response of the pituitary–thyroid axis under acute chromium‐induced stress condition to maintain homeostasis. The long‐term Cr(VI) exposures, however, may lead to attenuation/exhaustion of the pituitary–thyroid axis and pose serious threat to fish health and affect their population. © 2013 Wiley Periodicals, Inc. Environ Toxicol 30: 621–627, 2015.     

Mycotoxin zearalenone induced gonadal impairment and altered gene expression in the hypothalamic–pituitary–gonadal axis of adult female zebrafish (Danio rerio)

In the present study, we aimed to assess the adverse effects of zearalenone (ZEA) at environmentally relevant concentrations (0.5, 1, 5 and 10 μg l^?1) on hypothalamic–pituitary–gonadal axis associated reproductive function using zebrafish model. ZEA was exposed to female zebrafish for 21 days to assess growth indices such as condition factor, hepatosomatic index, gonadosomatic index and caspase 3 activity. Further, expression of estrogen receptor (ER) α and CYP19a1b genes in the brain, ERα and vitellogenin (Vtg) genes in the liver and follicle‐stimulating hormone receptor, luteinizing hormone receptor, ERα, steroidogenic acute regulatory protein, 3β‐hydroxysteroid dehydrogenase (HSD), 17‐βHSD and CYP19a1 genes in the ovary were also investigated. Our results showed that there were no significant changes in the condition factor and hepatosomatic index, whereas a significant (P < .05) reduction in the gonadosomatic index, increase in caspase 3 activities and Vtg expression was observed at higher concentration. However, no significant changes were observed at lower treatment levels. Further, we also observed significant (P < .05) upregulation in ERα, Vtg, luteinizing hormone receptor, steroidogenic acute regulatory protein, 3β‐HSD, 17β‐HSD, CYP19a1 and CYP19a1b genes in treatment groups with higher levels of ZEA. Moreover, in histopathological examination, we observed oocyte atresia and oocyte membrane detachment in ovaries at the highest concentration. In conclusion, the present study revealed the negative impact of ZEA on zebrafish reproductive system by involvement of the hypothalamic–pituitary–gonadal axis‐associated reproductive function.     

The GnRH analogues affect novel neuropeptide SMIM20/phoenixin and GPR173 receptor expressions in the female rat hypothalamic–pituitary–gonadal (HPG) axis

The recently discovered peptide phoenixin (PNX) and its receptor GPR173 are novel factors that exhibit a large spectrum of regulatory activity, especially when considered as a central modulator of GnRH‐related hormonal control of reproductive processes. It has been already proven that GnRH agonists and antagonists can modulate peptidergic signalling in the HPG axis. Despite these findings, there is so far no information regarding the influence of treatment with GnRH analogues on SMIM20/phoenixin signalling in the hypothalamic–pituitary–gonadal axis. In the current study, SMIM20/phoenixin and GPR173 mRNA levels were measured in the hypothalamus, pituitary and ovaries of female rats in the dioestrus phase following treatment with GnRH‐R agonist (buserelin) and antagonist (cetrorelix) using quantitative real‐time PCR. The serum PNX concentrations were also estimated with ELISA technique. The hypothalamic, hypophyseal and especially ovarian levels of SMIM20 mRNA were increased after both buserelin and cetrorelix administration. The GPR173 expressions were in turn decreased in the hypothalamus and pituitary. Treatment with the GnRH analogues led to the modulation of SMIM20/phoenixin and GPR173 mRNA expression in the female rat hypothalamic–pituitary–gonadal axis. By identifying buserelin and cetrorelix as novel modulators of phoenixin signalling in the animal HPG axis, these results cast new light on the GnRH analogues mode of action and contribute to a better understanding of the mechanisms responsible for the hormonal control of reproduction.     

Simultaneous detection and quantitation of organic impurities in methamphetamine by ultra‐high‐performance liquid chromatography–tandem mass spectrometry,a complementary technique for methamphetamine profiling

The analysis of organic impurities plays an important role in the impurity profiling of methamphetamine, which in turn provides valuable information about methamphetamine manufacturing, in particular its synthetic route, chemicals, and precursors used. Ultra‐high‐performance liquid chromatography – tandem mass spectrometry (UHPLC – MS/MS) is ideally suited for this purpose due to its excellent sensitivity, selectivity, and wide linear range in multiple reaction monitoring (MRM) mode. In this study, a dilute‐and‐shoot UHPLC – MS/MS method was developed for the simultaneous identification and quantitation of 23 organic manufacturing impurities in illicit methamphetamine. The developed method was validated in terms of stability, limit of detection (LOD), lower limit of quantification (LLOQ), accuracy, and precision. More than 100 illicitly prepared methamphetamine samples were analyzed. Due to its ability to detect ephedrine/pseudoephedrine and its high sensitivity for critical target markers (eg, chloro‐pseudoephedrine, N‐cyclohexylamphetamine, and compounds B and P), more impurities and precursor/pre‐precursors were identified and quantified versus the current procedure by gas chromatography – mass spectrometry (GC – MS). Consequently, more samples could be classified by their synthetic routes. However, the UHPLC – MS/MS method has difficulty in detecting neutral and untargeted emerging manufacturing impurities and can therefore only serve as a complement to the current method. Despite this deficiency, the quantitative information acquired by the presented UHPLC – MS/MS methodology increased the sample discrimination power, thereby enhancing the capacity of methamphetamine profiling program (MPP) to conduct sample‐sample comparisons.     

Effects of 4‐nonylphenol on balance of steroid and thyroid hormones in sexually immature male yellowfin seabream (Acanthopagrus latus)

Nonylphenol (NP) is an endocrine disrupting chemical which has been shown to be able to modulate the endocrine system of various organisms by different mechanisms. The objective of this study was to investigate the potential effects of 4‐NP on steroid and thyroid hormone levels in sexually immature male yellowfin seabream (Acanthopagrus latus), a protandrous hermaphrodite species. For this, the fish were injected with ascending doses (10, 50, 100, and 200 μg g^?1 body weight) of 4‐nonylphenol (4‐NP) or vehicle during 2 weeks. After 7 and 14 days the fish were anesthetized, blood sample were collected and plasma steroid and thyroid hormone concentrations were quantified by radioimmunoassay. The result showed that 4‐NP induced a significant increase in 17β‐etradiol levels at dose 10 μg g^?1, while the levels of this hormone in the higher doses decreased compared with the control group. However, 4‐NP treatment did not have any significant effect on plasma levels of testosterone. In addition, it was observed that 4‐NP affect the level of thyroid hormones in fish. Plasma thyroxine levels increased in a dose‐dependent manner after 7 and 14 days of the exposure. In contrast, a significant decrease in triiodothyronine levels was observed during the experiment period. Moreover, no significant change was detected for thyroid stimulating hormone levels in 4‐NP‐treated fish. These results indicated that 4‐NP could lead to disturb the balance of steroid and thyroid hormones with potential consequences for sexually immature male yellowfin seabream. © 2012 Wiley Periodicals, Inc. Environ Toxicol 29: 459–465, 2014.     

The impact of prolonged cadmium exposure and co-exposure with polychlorinated biphenyls on thyroid function in rats

Endocrine-disrupting chemicals currently represent one of the major concerns and this study was aimed to investigate the effects of different doses of cadmium, widespread toxic metal, on the levels of thyroid hormones and to calculate Benchmark doses for these effects. Furthermore, the effects of co-exposure to cadmium and polychlorinated biphenyls on thyroid function were investigated. Six orally-treated groups of rats were receiving 0.3, 0.6, 1.25, 2.5, 5 and 10 mg Cd/kg b.w./day, five groups were orally treated with 0.5, 1, 2, 4 and 8 mg PCBs/kg b.w./day, while nine groups of rats were orally-treated with different dose combinations of Cd and PCBs (0.6, 1.25 and 2.5 mg Cd/kg b.w. and 2, 4 and 8 mg PCBs/kg b.w./day), during 28 days. Thyroid hormones were adversely affected by cadmium, with most prominent effect observed on triiodothyroxine levels indicating Cd interference with thyroid function at extrathyroidal level. Calculated Benchmark doses for Cd effects on thyroid hormones indicate triiodothyroxine as the most sensitive one that can be used as a basis for risk assessment. This study also implicates possible synergistic effects of Cd and PCBs on thyroid function as a consequence of their interference at different levels of thyroid homeostasis.     

Disruption of thyroid hormone homeostasis in Ugt1a-deficient Gunn rats by microsomal enzyme inducers is not due to enhanced thyroxine glucuronidation

Microsomal enzyme inducers (MEI) that increase UDP-glucuronosyltransferases (UGTs) are thought to increase glucuronidation of thyroxine (T₄), thus reducing serum T₄, and subsequently increasing thyroid stimulating hormone (TSH). Ugt1a1 and Ugt1a6 mediate T₄ glucuronidation. Therefore, this experiment determined the involvement of Ugt1a enzymes in increased T₄ glucuronidation, decreased serum T₄, and increased TSH after MEI treatment. Male Wistar and Ugt1a-deficient Wistar (Gunn) rats were fed a control diet or diet containing pregnenolone-16α-carbonitrile (PCN; 800 ppm), 3-methylcholanthrene (3-MC; 200 ppm), or Aroclor 1254 (PCB; 100 ppm) for 7 days. Serum T₄, triiodothyronine (T₃), and TSH concentrations, hepatic T₄/T₃ glucuronidation, and thyroid histology and follicular cell proliferation were investigated. PCN, 3-MC, and PCB treatments decreased serum T₄, whereas serum T₃ was maintained in both Gunn and Wistar rats (except for PCB treatment). TSH was increased in Wistar and Gunn rats after PCN (130 and 277%) or PCB treatment (72 and 60%). T₄ glucuronidation in Wistar rats was increased after PCN (298%), 3-MC (85%), and PCB (450%), but was extremely low in Gunn rats, and unchanged after MEI. T₃ glucuronidation was increased after PCN (121%) or PCB (58%) in Wistar rats, but only PCN increased T₃ glucuronidation in Gunn rats (43%). PCN treatment induced thyroid morphological changes and increased follicular cell proliferation in both strains. These data demonstrate that T₄ glucuronidation cannot be increased in Ugt1a-deficient Gunn rats. Thus, the decrease in serum T₄, increase in TSH, and increase in thyroid cell proliferation after MEI are not dependent on increased T₄ glucuronidation, and cannot be attributed to Ugt1a enzymes.     

Attempt to map the receptor binding sites of human follicle‐stimulating hormone using disulfide peptides of its β‐subunit indicates major involvement of the regions around disulfide bonds Cys28–Cys82 and Cys32–Cys84 in receptor binding of the hormone

Abstract: Follicle‐stimulating hormone (FSH) is a heterodimeric glycoprotein hormone secreted by the anterior pituitary. It plays a very important role in folliculogenesis in females and is responsible for spermatogenesis in males. The α‐subunit which is common within a species and the β‐subunit which is hormone‐specific are held together by noncovalent association. This association is very essential for the biological activity of the hormone. Each of these subunits are highly cross‐linked by disulfide bonds which appear to stabilize the tertiary structures required for the noncovalent association of the subunits to generate hormonal activity. This study was initiated to delineate the role of the disulfide bonds of hFSHβ in receptor binding of the hormone. Five intermolecular and one intramolecular disulfide peptides corresponding to the disulfide bonds found in hFSHβ were synthesized and screened along with their linear counterparts, for their ability to competitively inhibit the radiolabelled [¹²⁵I]hFSH from binding to the FSH receptor containing membranes from the testis of immature rats. The disulfide peptides Cys²⁸–Cys⁸² and Cys³²–Cys⁸⁴ were found to be the most potent in inhibiting radiolabelled hFSH from binding to its receptor. The results suggest the involvement of the regions around disulfide bonds Cys²⁸–Cys⁸² and Cys³²–Cys⁸⁴ in receptor binding of the hormone. The studies also suggest the involvement of βL2 and βL3 loop regions in receptor binding of the hormone. This study is the first of its kind to use disulfide peptides rather than linear peptides to map the receptor binding regions of hFSH.     

Effects of decabromodiphenyl ether (BDE‐209) on mRNA transcription of thyroid hormone pathway and spermatogenesis associated genes in Chinese rare minnow (Gobiocypris rarus)

Polybrominated diphenyl ethers (PBDEs) are widely used as flame retardants, which are ubiquitous environmental contaminant found in both abiotic and biotic environmental samples. Deca‐BDE (BDE‐209) is the principal component, which is currently used worldwide. In this study, the effect of BDE‐209 on the mRNA levels of thyroid hormone (TH) related genes and spermatogenesis associated genes were determined from larvae and adult rare minnow (Gobiocypris rarus) exposed to concentrations 0.01, 0.1, 1, and 10 μg/L for 21 days. The results showed that the type II deiodinase (dio2) and sodium iodide symporter (nis) mRNA levels were significantly up‐regulated in the larvae at 10 μg/L treatment. In adult, histopathological observations showed that liver of female fish were degenerated at 10 μg/L treatment, and inhibition of spermatogenesis were observed in testis of male fish. In addition, the thyroid hormone receptor α (trα), dio2, and nis mRNA levels in the liver of male and female fish were significantly up‐regulated, whereas dio2 and nis mRNA levels were significantly down‐regulated in the brain. These results indicate that exposure to BDE‐209 could result in tissue‐specific alternations of TH‐related genes expression in adults. Moreover, the mRNA levels of the testis‐specific apoptosis genes, the spermatogenesis‐associated 4 (spata4) and spermatogenesis‐associated 17 (spata17), were down‐regulated at 10 μg/L treatment in testis of male fish. Our results suggest that BDE‐209 may pose threat to normal thyroid and reproductive function in fish. © 2011 Wiley Periodicals, Inc. Environ Toxicol 29: 1–9, 2014.     

Absence of adverse effect on thyroid function and red blood cells in a population of workers exposed to cobalt compounds

Context

Hypothyroidism has been observed in the fifties and sixties as an undesirable side-effect of cobalt therapy used for its erythropoietic properties in the treatment of anemia.

Objective

This study aims at evaluating the possible impact of both cumulative (long-term) and recent occupational exposure to cobalt on thyroid function and red blood cells.

Methods and setting

A cross-sectional survey was conducted from February 2008 to August 2009 in a population of 249 male workers from a cobalt production department in the North of Belgium. The possible effect of cobalt exposure on thyroid and red blood cells was investigated through multiple regression analyses.

Results

Blood cobalt ranged from undetectable to 3.20 μg/100 ml (median 0.10); urinary cobalt from 0.30 to 204.30 μg/g_creat (median 3.90) and long-term exposure to cobalt ranged from 0.15 to 6990.46 μg/g_creat·years (median 106.09). No effect of cobalt exposure on thyroid or red blood cell parameters was observed at these levels of exposure.

Conclusion

The results support the absence of effects on the thyroid and red blood cells when occupational exposure to cobalt is kept below the recommended biological limit of occupational exposure (15 μg Co/g_creat in urine).     

A study of the role of DIO1 and DIO2 polymorphism in thyroid cancer and drug response to therapy in the Saudi population

BackgroundDeiodinases comprise a group of selenoproteins that regulate the bioavailability of active thyroid hormones (TH) in a time and tissue specific fashion. They increase the hormonal activity by metabolizing their inactive precursors to active forms or terminate their activity by deactivating active hormones. The role of the deiodinase (DIO) gene polymorphisms in thyroid cancer is not fully understood yet. This study evaluated the potential association of the DIO1 and DIO2 genes with differentiated thyroid cancer and differential thyroxine dose requirement in thyroidectomized patients in a Saudi cohort.MethodsWe selected four variants (one DIO1 and three DIO2) for the association studies using Taqman assays in 507 DTC patients undergoing treatment with thyroxin against 560 disease-free individual, all of Saudi Arab origin.ResultsNone of the studied variants was linked to differentiated thyroid cancer. The rs1388378_G > T was initially linked to thyroxine dose requirement (p = 0.035) when all patients were considered together, but this association was lost when the patients were classified into either near suppressed (0.1 ≤ TSH < 0.5) or suppressed (TSH < 0.1) TSH group.DiscussionAlthough the results suggest only a weak relationship with differentiated thyroid cancer, they strongly indicate that the DIO2 polymorphism influences the hormonal dose requirement in patients undergoing treatment with thyroxine. This probably points to a distinction in the way this gene influences disease as compared to therapy thereof.