Cardiac Malformations in Congenital Hypothyroidism: A Case Report

Introduction: Congenital hypothyroidism is the most common causes of preventable mental retardation. It is associated with other births defects like cardiac malformations. Descriptions in Sub Saharan Africa are rare, justifying the present report. Case Report: We reported the cases of 3 female patients, diagnosed with hypothyroidism, presenting in addition pulmonary stenosis. The diagnosis was late in all the patients and we noticed clinical improvement under levothyroxine. Conclusion: Association congenital hypothyroidism and cardiac defect is not rare. Our patients are female with no history of consanguinity, presenting congenital hypothyroidism with a gland in situ associated with pulmonary stenosis. Systematic screening of other births defects is thus recommended in affected patients.

The Correlation between Free Triiodothyronine, Free Thyroxine and Hypertension in Depression Patients with Hypothyroidism and Its Clinical Guiding Value

Background: Cardiovascular diseases, such as hypertension and coronary heart disease, are often accompanied by thyroid and mental diseases, the harm of which poses great threats to patients’ health. Objective: To explore the correlation between free triiodothyronine (FT3), free thyroxine (FT4) and hypertension in depression patients with hypothyroidism and its clinical guiding value. Methods: A total of 548 patients diagnosed with hypothyroidism in Wuxue First People’s Hospital of Hubei Province from January 2018 to September 2022 were enrolled. According to whether complicated with depression, they were divided into hypothyroidism without depression group (group A) and hypothyroidism with depression group (group B). The gender, age, comorbidities (such as depression, hypertension, diabetes, dyslipidemia, acute myocardial infarction), FT3, FT4, and thyroid stimulating hormone (TSH) levels were recorded. Spearman rank correlation was used to analyze hypertensive patients with hypothyroidism. Multivariate binary Logistic regression was used to analyze the influencing factors of hypertension in patients with hypothyroidism. Results: The TSH level, the number of hypertension, coronary heart disease and hyperlipidemia in group B were statistically significantly higher than those in group A (P 3 level in group B was statistically significantly lower than that in group A (P s = 0.092), coronary heart disease (rs = 0.000), hyperlipidemia (rs = 0.000), diabetes (rs = 0.000), and age (rs = 0.000), and negatively correlated with FT3 (rs = 0.000) (P 3 and FT4 were the influencing factors of hypertension. The risk of hypertension in patients with coronary heart disease and hyperlipidemia significantly increased by 3.425 and 1.761 times (P 3, the risk of hypertension increased (P 4, the risk of hypertension significantly increased (P 3 and FT4 are the influencing factors of hypertension. The lower the FT3 level, the higher the FT4 level, the higher the risk of hypertension. FT3 and FT4 may be potential biomarkers of depression in hypertensive patients. Thyroid function assessment is recommended in patients with hypertension.

Correlation Study of Aortic Velocity Propagation, Abdominal Aortic Intima-Media Thickness, and Epicardial Adipose Tissue Thickness in Subclinical Hypothyroidism Patients

Objective:To explore the correlation between epicardial fat thickness(EFT),aortic velocity propagation(AVP),and abdominal aortic intima-media thickness(AA-IMT)in patients with subclinical hypothyroidism(SH).Additionally,to compare these indicators between SH patients and healthy individuals,providing a new theoretical basis for the clinical prevention and treatment of cardiovascular diseases.Method:Clinical data from 50 SH patients(23 males and 27 females)and 50 healthy outpatient examinees(22 males and 28 females)were analyzed.The participants were selected from January 2022 to December 2023 at Loudi Central Hospital.EFT,AVP,and AA-IMT were measured,and their correlations were analyzed.Results:SH patients had significantly higher EFT and AA-IMT levels than the control group,while their AVP was significantly lower,with these differences being statistically significant(P<0.05).Correlation analysis revealed a significant negative correlation between EFT and AVP(P<0.001),a significant positive correlation between EFT and AAO-IMT(P<0.001),and a significant negative correlation between AVP and AAO-IMT(P<0.001).Multivariate binary logistic regression analysis identified increased EFT,decreased AVP,and increased AAO-IMT as independent risk factors for SH patients.Conclusion:In SH patients,EFT and AAO-IMT are elevated,whereas AVP is reduced.EFT and AVP are significantly correlated with AAO-IMT.EFT and AAO-IMT can serve as reliable indicators for evaluating subclinical atherosclerosis in SH patients,providing a diagnostic basis for clinical practice.

Traditional Chinese medicine prescriptions and herbs for the treatment of hypothyroidism:a narrative review

The increasing prevalence of hypothyroidism,which can cause endocrine dysfunction,abnormal neurological function,and cardiovascular and cerebrovascular injuries,poses serious health problems.Thyroid hormone supplementation constitutes the current main therapeutic method for hypothyroidism,yet it has many limitations and risks and is not suitable for everyone.Therefore,it is necessary to seek alternative and complementary treatment methods.It has been proven in practice that traditional Chinese medicine(TCM)possesses multi-channel comprehensive characteristics for the treatment of hypothyroidism and has more advantages than single thyroid hormone supplementation.Through a comprehensive examination of existing literature about TCM efficacy in addressing hypothyroidism,we have meticulously consolidated the most recent research findings on prescriptions and herbal substances employed in the treatment of this condition.Furthermore,we have explicated their respective functions in the management of hypothyroidism,thereby offering valuable perspectives and recommendations for the prospective utilization of natural remedies in its treatment.

Mechanism of intervention of medicine combined with mild moxibustion on hypothyroidism rat model

Objective:To explore the intervention effect of medicine combined with mild moxibustion on immune factor and Na/I symporter(NIS)in hypothyroidism rat model.Methods:The model was successfully made by intragastric administration of propylthiouracil(PTU)solution medicine and medicine combined with mild moxibustion groups were given levothyroxine sodium suspension 60μg/kg body weight by gavage,once a day.In the medicine combined with mild moxibustion group,mild moxibustion was applied in“Dazhui”,“Mingmen”,“Pishu”,“Shenshu”,and 10 minutes per point,once a day,and one day off every six days;four weeks in a row.The model group and medicine was fixed in the same way as the medicine combined with mild moxibustion group.The blank group received no treatment.The contents of thyrotropin-releasing hormone(TSH),tatalthyroxine(TT4),thyroid peroxidase antibody(TPOAb),thyroglobulin antibodies(TGAb),Interleukin-4(IL-4)and Interleukin-23(IL-23)in serum were determined by Enzyme Linked Immunosorbent Assay(ELISA).The content of NIS and the expression level of NISmRNA in thyroid tissues of each group were detected by immunohistochemistry and real-time polymerase chain reaction(R-T PCR).Results:Compared with the blank group,the contents of TSH,TPOAb,TGAb and IL-23 in the serum of rats in the model group were increased,the contents of IL-4 and TT4 were decreased,and the contents of NIS and NISmRNA in thyroid tissue were decreased,with statistical significance(P<0.01).Compared with model group,the contents of TSH,TPOAb,TGAb and IL-23 in serum of medicine group and medicine combined with mild moxibustion group were decreased,while the contents of IL-4 and TT4 were increased;the NIS content and NISmRNA expression in thyroid tissues were increased,and the differences were statistically significant(P<0.01).Compared with the medicine group,NISmRNA expression in thyroid tissues of medicine combined with mild moxibustion groups was increased,and the difference was statistically significant(P<0.05).Conclusion:Medicine combined with mild moxibustion can decrease the contents of TPOAb,TGAb and IL-23,and increase the content of IL-4,increasing the content and expression of NIS to interfere with the hypothyroidism rat model.

Spontaneous ovarian hyperstimulation syndrome and pituitary hyperplasia mimicking macroadenoma associated with primary hypothyroidism

We report an unusual case of spontaneous ovarian hyperstimulation syndrome and pituitary hyperplasia mimicking macroadenoma in an adult,non-pregnant woman.Her condition was triggered by unrecognized primary hypothyroidism,which regressed after thyroid hormone replacement therapy.This case highlights the need for clinicians and radiologists to familiarize themselves with the clinical and imaging features detected in case of these complications of primary hypothyroidism,which are not well known in the medical and radiological profession.Such improved knowledge will help avoid delays in diagnosis,progression to lifethreatening complications,and unnecessary surgery.

Subclinical Hypothyroidism and Isolated Hypothyroxinemia during Pregnancy and Their Association with Pregnancy Outcome: A 2-Year Study

INTRODUCTION: Overt hypothyroidism in pregnancy is associated with adverse outcomes, but the effects of subclinical hypothyroidism and isolated hypothyroxinemia on pregnancy outcomes are still controversial. Subclinical hypothyroidism might be associated with preterm delivery, low Apgar score, fetal death and miscarriages and isolated hypothyroxinemia with preterm labor, high birth weight and neurocognitive deficits in children. Other studies show no association with any complications at all. In the present study we tried to estimate whether maternal subclinical hypothyroidism and isolated hypothyroxinemia are associated with complications during pregnancy in our population which represents the pregnant population of Western Greece. METHODS: In a total of 469 pregnant women, third trimester serum was assayed for thyroid-stimulating hormone (TSH) and free thyroxine (free T4). Thyroid hypofunction was defined as 1) subclinical hypothyroidism with TSH levels above 3 mIU/L for the 3rd trimester and normal free T4 and 2) isolated hypothyroxinemia with TSH levels below 3 mIU/L for the 3rd trimester and free T4 below the 5th percentile. The results were associated with birth weight, week of labor, history of miscarriages and demographic characteristics. Patients with thyroid hypofunction were compared with euthyroid patients (TSH and free T4 between normal limits). The results were analyzed with one-way ANOVA and χ2 test. RESULTS: Subclinical hypothyroidism was documented in 10.9% and isolated hypothyroxinemia in 21.7% of pregnant women. Subclinical hypothyroidism was not associated with birth weight, week of labor, or history of miscarriages. On the contrary, hypothyroxinemia was associated with high birth weight (P < 0.05). CONCLUSION: In our study, we did not find a link between subclinical hypothyroidism and adverse pregnancy outcomes. Similarly, hypothyroxinemia was not associated with pregnancy complications. However, it was associated with higher birth weight. Our studies contribute to our understanding, whether or not subclinical hypothyroidism and isolated hypothyroxinemia are associated with pregnancy adverse outcomes and whether treatment and test for hypothyroidism should become routine during pregnancy.

Treatment and follow-up of children with transient congenital hypothyroidism

Objective： To study the clinical therapy and prognosis in children with transient congenital hypothyroidism （CH）. Methods： Fifty-seven children with CH diagnosed after neonatal screening were treated with low-dosage levothyroxine （L-T4）. Follow-up evaluation included the determination of TT3, TT4 and TSH serum levels and the assessment of thyroid gland morphology, bone age, growth development and development quotients （DQ）. A full check-up was performed at age 2, when the affected children first discontinued the L-T4 treatment for 1 month, and one year later. Development quotients were compared with a control group of 29 healthy peers. Results： The initial L-T4 dosage administered was 3.21-5.81μg/（kg·d） with an average of （16.25±3.87）μg/d. Mean duration of therapy was （28.09±9.56） months. No significant difference was found between study group and control group in the DQ test （average score （106.58±14.40） vs （102.4±8.6）, P〉0.05） and 96.49% of the CH children achieved a test score above 85. Bone age, 99mTc scans and ultrasonographic findings were all normal, and evaluation of physical development was normal too, as were the serum levels of TT3, TT4 and TSH after one year of follow-up. Conclusion： AL-T4 dosage of 3.21-5.81μg/（kg·d） was found sufficient for the treatment of transient CH. The treated children showed satisfactory overall mental and physical development at age 2. So it is possible for CH children to stop taking medicine if their laboratory findings and physical development are all normal after regular treatment and 2-3 years of follow-up.

Effect of treatment of overt hypothyroidism on insulin resistance

AIM: To investigate the impact of hypothyroidism and thyroxine therapy on insulin sensitivity in patients with overt hypothyroidism.METHODS: The study included twenty seven overtly hypothyroid and fifteen healthy euthyroid South Western Asian females.Both groups had matching age and body mass index.Physiological and pathological conditions as well as medications that may alter thyroid function,glucose homeostasis or serum lipids were ruled out.Serum thyrotropin(TSH),free tetraiodothyronine(FT4),free triiodothyronine(FT3),fasting insulin(FI),fasting plasma glucose(FPG),total cholesterol and triglycerides were measured before and six months after initiating thyroxine therapy for hypothyroid patients and once for the control group.Insulin resistance(IR) was estimated using homeostasis model assessment(HOMA-IR) and Body mass index(BMI) was calculated.RESULTS: Both study groups,hypothyroid patients and euthyroid control subjects,had matching age and body mass index(P-value 0.444,0.607 respectively).No significant difference was found between the hypothyroid patients and the euthyroid control group regarding fasting plasma glucose,fasting insulin,insulin resistance,total cholesterol and triglycerides(P-values 0.432,0.621,0.883,0.586,0.05 respectively).In the hypothyroid patients,triglycerides showed direct correlation to TSH and inverse correlation to FT3.Similarly total cholesterol inversely correlated to FT3 but its direct correlation to TSH did not reach statistical significance.After thyroxine replacement and reaching an euthyroid state as confirmed by clinical and laboratory data,there was no significant change in fasting plasma glucose,insulin resistance or triglyceride level(P-value 0.216,0.204,0.175 respectively) while total cholesterol significantly decreased(P-value 0.043) and fasting insulin significantly increased(P-value 0.047).CONCLUSION: Hypothyroidism has no impact on insulin sensitivity.Correction of hypothyroidism is not associated with a significant change of insulin sensitivity or triglycerides,but with a significant reduction of total cholesterol.

Colonic duplication in an adult who presented with chronic constipation attributed to hypothyroidism

Gastrointestinal duplications are an uncommon congenital abnormality that manifest before the age of two in 80% of cases. Ileal duplication is the most common while colonic duplication, either cystic or tubular, occurs in 10%-15% of cases and remains asymptomatic and undiagnosed in most cases. Mostly occurring in pediatric patients, colonic duplication is encountered in adults in only a few cases. The most common clinical manifestations are abdominal pain and intestinal obstruction. Rarely, duplications present with signs of acute abdomen or acute bleeding. This study reports a case of colonic duplication in an adult who presented with chronic constipation. Complete diagnostic workup was made on several occasions during the previous eight year period, but no pathology was found and chronic constipation was attributed to hypothyroidism caused by long standing Hashimoto thyroiditis. Nultislice CT, performed because of abdominal distension, defined colonic pathology but the definite diagnosis of duplication of the transversal colon was made at operation. The cystic duplication and the adjacent part of the ascending and transversal colon were excised enblock. This study implies that colonic duplication, though uncommon, should be included in the differential diagnosis of chronic constipation even when precipitating factors for constipation, such as hypothyroidism are present.

Hypothyroidism in patients with autoimmune pancreatitis

AIM To examine thyroid function and clinical features of hypothyroidism in autoimmune pancreatitis(AIP) patients.METHODS We examined thyroid function in 77 patients with type 1 AIP(50 males, 27 females; median age 68 years, range 33-85) diagnosed according to the Japanese diagnostic criteria for AIP 2011. We compared clinical and serological findings between patients with and without various categories of hypothyroidism. The change in hypothyroidism after steroid therapy was also examined. RESULTS Eight patients(10%) had hypothyroidism of 6 patients had subclinical hypothyroidism with a normal serum free thyroxine(FT4) and high thyroid stimulating hormone(TSH) level, and 2 patients had central hypothyroidism with low serum free triiodothyronine(FT3), FT4 and TSH levels. A significant goiter of the thyroid was not observed in any patient. There were no significant differences in age; male to female ratio; serum concentrations of IgG and IgG 4-related disease(IgG4-RD); presence of antithyroglobulin antibody, antinuclear antigen or rheumatoid factor; or presence of extrapancreatic lesions between the 6 patients with subclinical hypothyroidism and patients with euthyroidism. After steroid therapy, both subclinical and central hypothyroidism improved with improvement of the AIP.CONCLUSION Hypothyroidism was observed in 8(10%) of 77 AIP patients and was subclinical in 6 patients and central in 2 patients. Further studies are necessary to clarify whether this subclinical hypothyroidism is another manifestation of IgG4-RD.

Hypothyroidism during pregnancy: Controversy over screening and intervention

Thyroid hormones are critical for foetal neurological development and maternal health. Maternal hypothyroidism during pregnancy is associated with adverse impact on health of the mother as well as the progeny. Reduced thyroid hormone levels predispose the child to develop mental retardation and cognitive delay in early life. In the mother, hypothyroidism during pregnancy is associated with spontaneous abortion, placental abruption, preterm delivery and hypertensive disorders. Therefore, screening and therapeutic intervention is justified to prevent foetal as well as maternal co-morbidities. In view of impact of such a large-scale screening and intervention program on limited healthcare resources, it is debatable if a targeted rather than universal screening program will result in comparable outcomes. In addition, there is an ongoing debate regarding best evidence-based practice for the management of isolated hypothyroxinaemia, subclinical hypothyroidism and euthyroid women with autoimmune hypothyroidism. We have carried out a review of the literature; firstly, to determine whether universal screening for asymptomatic women in early pregnancy would be cost-effective. Secondly, we have retrospectively reviewed the literature to analyse the evidence regarding the impact of therapeutic intervention in women with subclinical hypothyroidism.

Elevated airborne beta levels in Pacific/West Coast US States and trends in hypothyroidism among newborns after the Fukushima nuclear meltdown

Various reports indicate that the incidence of congenital hypothyroidism is increasing in developed nations, and that improved detection and more inclusive criteria for the disease do not explain this trend entirely. One risk factor documented in numerous studies is exposure to radioactive iodine found in nuclear weapons test fallout and nuclear reactor emissions. Large amounts of fallout disseminated worldwide from the meltdowns in four reactors at the Fukushima-Dai-ichi plant in Japan beginning March 11, 2011 included radioiodine isotopes. Just days after the meltdowns, I-131 concentrations in US precipitation was measured up to 211 times above normal. Highest levels of I-131 and airborne gross beta were documented in the five US States on the Pacific Ocean. The number of congenital hypothyroid cases in these five states from March 17-December 31, 2011 was 16% greater than for the same period in 2010, compared to a 3% decline in 36 other US States

Hypothyroidism affects astrocyte and microglial morphology in type 2 diabetes

In the present study, we investigated the effects of hypothyroidism on the morphology of astrocytes and microglia in the hippocampus of Zucker diabetic fatty rats and Zucker lean control rats. To induce hypothyroidism, Zucker lean control and Zucker diabetic fatty rats at 7 weeks of age orally received the vehicle or methimazole, an anti-thyroid drug, treatment for 5 weeks and were sacrificed at 12 weeks of age in all groups for blood chemistry and immunohistochemical staining. In the me- thimazole-treated Zucker lean control and Zucker diabetic fatty rats, the serum circulating triiodo- thyronine （T3） and thyroxine （＇I＂4） levels were significantly decreased compared to levels observed in the vehicle-treated Zucker lean control or Zucker diabetic fatty rats. This reduction was more prominent in the methimazole-treated Zucker diabetic fatty group. Glial fibrillary acidic protein im- munoreactive astrocytes and ionized calcium-binding adapter molecule 1 （Iba-1）-immunoreactive microglia in the Zucker lean control and Zucker diabetic fatty group were diffusely detected in the hippocampal CA1 region and dentate gyrus. There were no significant differences in the glial fibril- lary acidic protein and Iba-1 immunoreactivity in the CA1 region and dentate gyrus between Zucker lean control and Zucker diabetic fatty groups. However, in the methimazole-treated Zucker lean control and Zucker diabetic fatty groups, the processes of glial fibrillary acidic protein immunoreac- tive astrocytes and Iba-1 immunoreactive microglia, were significantly decreased in both the CA1 region and dentate gyrus compared to that in the vehicle-treated Zucker lean control and Zucker diabetic fatty groups. These results suggest that diabetes has no effect on the morphology of as- trocytes and microglia and that hypothyroidism during the onset of diabetes prominently reduces the processes of astrocytes and microglia.

Diabetes mellitus and hypothyroidism: Strange bedfellows or mutual companions?

Clinicians should be cognizant of the close relationship that exists between two of the most common endocrine disorders, primary hypothyroidism and diabetes mellitus. This applies to patients with both type 1 and type 2 diabetes mellitus(T1DM and T2 DM respectively). However, the association is greater in T1 DM, probably because of the shared autoimmune predisposition. In patients with T2 DM, the relationship is somewhat weaker and the explanation less clear-cut. Factors such as dietary iodine deficiency, metformin-induced thyroid stimulating hormone suppression and poor glycemic control may all be implicated. Further translational research is required for greater clarification. Biochemical screening for abnormal thyroid function in individuals who have diabetes is warranted, particularly in females with T1 DM, and therapy with L-thyroxine appropriately instituted if hypothyroidism is confirmed.

Subclinical hypothyroidism is associated with lipid-rich plaques in patients with coronary artery disease as assessed by optical coherence tomography

Background Subclinical hypothyroidism （SCH） has recently been acknowledged as an unconventional risk factor for coronary artery disease （CAD） and characterized by poor prognosis, which may be due to atherosclerotic plaque characteristics. We conducted this study to observe coronary plaque characteristics in coronary artery disease patients with concomitant SCH. Methods Patients with coronary artery disease were enrolled in the study and divided into an SCH group （patients, n = 26; plaques, n = 35） and a non-SCH group （patients, n = 52; plaques, n = 66）. They were divided 1：2 according to propensity-matched analysis including age, diabetes mellitus, gender, CAD severity and culprit vessel. Optical coherence tomography （OCT） imaging was performed on all patients, and images were analyzed by two inde- pendent investigators. Lipid-rich plaques （LRP）, the precursor of vulnerable plaques, were defined as having more than one quadrant occu- pied with lipid pool. Maximum lipid arcs were simultaneously recorded. Fibrotic plaques and calcific plaques were also identified. The pres- ence of coronary dissection, plaque erosion, thrombus, macrophage, calcific nodule, thin-cap fibroatheroma and micro channel were all noted. Results The ratio of LRP in SCH group was significantly higher than that in non-SCH group （54% vs. 30.3%, P = 0.037）. That was the case as well for the maximum lipid arcs value （181.5°± 61.6° vs. 142.1° 4± 35.9°, p = 0.046）. While thin-cap fibroatheroma （TCFA） was detected, no difference was identified between the two groups in either TCFA ratio （20% vs. 16.7%, P = 0.579） or fibrous cap thickness （57.5 4± 14.0 vs. 63.5 4±10.7 gin, P = 0.319）. Other OCT characteristics such as dissection, plaque erosion, thrombus, macrophage shadow and calcific nodule were also similar. ConcLusion Higher ratio of LRP with greater lipid arc in SCH patients may be related to the plaque instability and poor prognosis in CAD patients with SCH.

A concomitant review of the effects of diabetes mellitus and hypothyroidism in wound healing

This paper reviews the negative impact of diabetes mellitus or hypothyroidism on wound healing, both in experimental and clinical settings. Since both are metabolic disorders of great clinical importance, special attention is given, not only to their pathophysiology, but also to their biochemical and histological effects on tissue integrity and regeneration. Also, special focus is awarded on wound healing of the gastrointestinal tract, i.e. in intestinal anastomosis, and how these disorders can lead to wound dehiscence. Since diabetes mellitus and hypothyroidism can coexist in clinical settings, more research must be directed on their influence on wound healing, considering them as one clinical entity.

Drug-Induced Hypothyroidism during Anti-Tuberculosis Treatment of Multidrug-Resistant Tuberculosis: Notes from the Field

We followed 188 euthyroidic persons undergoing treatment for multidrug resistant tuberculosis (MDR-TB) in the state of Karnataka, India to determine the incidence of hypothyroidism during anti-tuberculosis treatment. Overall, among MDR-TB patients with valid thyroid stimulating hormone (TSH) values, about 23% developed hypothyroidism (TSH value ≥10 mIU/ml) during anti-tuberculosis treatment;the majority (74%) occurring after 3 months of treatment. Among 133 patients who received a regimen that contained ethionamide, 42 (32%) developed hypothyroidism. Among 17 patients that received a regimen that contained para-aminosalicylate sodium, 6 (35%) developed hypothyroidism. Among 9 HIV positive patients on antiretroviral treatment, 4 (44%) developed hypothyroidism. These results differ from previously reported 4% incidence of hypothyroidism amongst patients who passively reported thyroidal symptoms during treatment, suggesting routine serologic monitoring of TSH throughout the course of treatment for MDR-TB is warranted.

A Case of Pleural Effusion Caused by Hypothyroidism

A case of primary hypothyroidism caused by pleural effusion was reported in order to improve the understanding of hypothyroidism and avoid or reduce misdiagnosis and treatment.

Inhibited 131I Uptake but Normal Release of Thyroid Hormone by Thyroid Gland in Response to TSH Administration in Subclinical Hypothyroidism

Background: Subclinical hypothyroidism is characterized by normal circulating thyroid hormone levels with super-normal TSH concentrations in absence of clinical manifestations. In majority of subjects, an etiologic factor is often identified. Moreover, therapy with levothyroxine normalizes serum TSH concentration while maintaining normal thyroid hormone concentrations. However, the exact pathophysiology of these thyroid hormone alterations is not well defined. Objective: Major steps in synthesis i.e. iodine uptake and the release of thyroid hormones in response to SC TSH administration were assessed in subjects with subclinical hypothyroidism. Methods: 10 men and 5 women with subclinical hypothyroidism, ages 42 - 76 years and 10 euthyroid men (39 - 70 years) participated. 24 hr 131Iodine thyroid uptake and serum T3, T4 and TSH concentrations were determined prior to and after SC administration of recombinant human TSH, 0.9 mg for two consecutive days. Comparisons were conducted for 24 hour uptake values as well as serum T3, T4 and TSH levels obtained prior to and after TSH administration. Results: In subjects with subclinical hypothyroidism 24 hour 131I thyroidal uptakes were normal (10% - 30%). However, the mean value was significantly lower, (p 3 and T4 concentrations in subjects with subclinical hypothyroidism were not significantly different in comparison to normal subjects. Serum TSH concentrations were supernormal and therefore were significantly higher in subjects with subclinical hypothyroidism in comparison to normal subjects and rose markedly in both groups following TSH administration with no significant difference among groups. Serum T4 and T3 rose significantly from PreTSH levels in both groups (p 131I Thyroid uptake is inhibited prior to as well as following SC TSH administration in comparison to normal subjects with maintenance of normal hormone release.