The thyrotrophic role of human chorionic gonadotrophin (hCG) in the early stages of twin (versus single) pregnancies
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Human chorionic gonadotrophin (hCG) is known to possess thyroid-stimulating activity. The aim of the present study was to assess the role of hCG in stimulating the maternal thyroid gland in the early stages of normal gestation.Thirty euthyroid healthy women were investigated prospectively. In each, conception had been assisted by in vitro fertilization techniques, which allowed for the precise determination of gestational age. Women were subdivided into single (n = 17) and twin (n = 13) pregnancies. Serum intact hCG and its free alpha and beta subunits, TSH and free T4 concentrations were measured at 6, 8, 9, 10, 11, 15, 19, 22 and 32 weeks.In twin pregnancies compared with single pregnancies, peak hCG concentrations (9-11 weeks) were significantly higher (mean +/- SE 171,000 +/- 12,500 vs 65,500 +/- 7600 U/l; P < 0.001), and also much more prolonged. Human CG concentrations above 75,000 U/l lasted for less than 1 week in single, compared with up to 6 weeks in twin pregnancies. Free beta-hCG subunit concentrations paralleled those of intact hCG in both groups. The ratios of free beta-hCG subunit/total hCG were similar in single and twin pregnancies, and did not vary with gestation time. Concerning thyroid function, twin pregnancy was more frequently associated with a lowering of TSH, which was also more profound than in single pregnancies. Furthermore, while free T4 levels remained normal in single pregnancies, they were transiently supranormal (up to 52 pmol/l) in four twin pregnancies.In twin pregnancies the placenta produces larger amounts of hCG for a prolonged period of time than in single pregnancies. Both the amplitude and duration of hCG production (i.e. the global exposure of the thyroid gland to hCG) are responsible for increased thyroidal stimulation, leading more frequently to increased free T4 and suppressed TSH levels. The results emphasize the role of hCG in stimulating maternal thyroid function in the first trimester of pregnancy. Even though the production of a variant hCG molecule with potent thyrotrophic activity cannot be excluded, this hypothesis is not required to explain the data. Clinicians should be aware of the frequent occurrence of significant but transient biochemical hyperthyroidism associated with hCG stimulation in the early stages of gestation, particularly in twin pregnancies.Keywords:
Twin Pregnancy
A new method for assessing both glucose utilization and response to insulin is presented. The technique eliminates certain shortcomings of previous methods, which have yielded widely varying results in patients with abnormal thyroid function. The results of the application of the new procedure to 38 euthyroid patients, 15 patients with hyperthyroidism and 13 patients with hypothyroidism, are presented. In the euthyroid group, the mean specific rate constant for glucose utilization (K) was .0349; for the hyperthyroid patients it was .0325; and for the hypothyroid patients it was .0269. The mean K value for the hypothyroid patients was significantly less than that for the euthyroid patients, whereas the mean K value for the hyperthyroid patients was not significantly different from that for the euthyroid patients. In the euthyroid group, insulin resulted in a mean increase in K of 59 per cent. The hyperthyroid patients showed a significantly greater response (+ 104 per cent) to insulin. The hypothyroid patients showed an insignificant response (+ 18 per cent) to insulin. The interpretation of these results is discussed with regard to other data on the relationship of thyroid function to carbohydrate metabolism.
Carbohydrate Metabolism
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Studies of thyroid function after diet-induced weight loss in patients with obesity have yielded conflicting results. It is not known whether adding exercise to diet affects thyroid function in this patient population. The aim of the study was to prospectively evaluate the effects of a rehabilitation program on weight, body composition and thyroid function in euthyroid patients with obesity.Serum levels of thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) in euthyroid patients with severe obesity were analyzed before and at the end of a 3-month rehabilitation program. Relationships between body weight or composition and changes in thyroid function were also investigated. Each study participant acted as his/her own control.The study population consisted of 34 euthyroid patients with obesity (18 men and 16 women; mean ± SD age: 51 ± 12). The mean BMI was 49.3 ± 12.4 kg/m2 before the program and 46 ± 10.8 (p < 0.005) at the end, with a mean body weight loss of 11 kg (p < 0.05) and a mean fat mass loss of 6.8 kg (p < 0.05). The weight and fat mass losses were not significantly correlated with the serum concentrations of TSH, FT3 and FT4 measured at the end of the program.A 3-month rehabilitation program combining diet and exercise produced weight and fat mass losses without inducing thyroid dysfunction in patients with obesity.
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The pharmacokinetics of propylthiouracil (PTU) was studied in 7 patients having Graves' disease when they were hyperthyroid and then again when they were euthyroid. Two additional euthyroid patients were also studied. The t1/2, Ke, Ka, apparent Vd, AUC and clearance were calculated. Serum T3 and T4 were also measured. PTU had an immediate effect in reducing T3 levels. Although there were intraindividual variations, the mean PTU elimination half-time did not change from the hyperthyroid state (1.47 h) to the euthyroid state (1.53 h). The mean Ka when hyperthyroid (2.12 h-1) was significantly increased (p less than 0.005) compared to when euthyroid (1.00 h-1). The calculated kinetic information indicates that the disposition of PTU in children is similar to that reported in adults.
Propylthiouracil
Antithyroid agent
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Objective To analyze the natural changes of maternal thyroid function among women with subclinical thyroid dysfunction and euthyroid women during pregnancy.Methods A total of 4 042 singleton pregnant women received routine antenatal care in the Obstetrics and Gynecology Hospital of Fudan University between April and November 2012 were enrolled.Thyroid-stimulatinghormones (TSH),freetriiodothyronine (FT3) and free thyroxine (FT4) of 7 136 samples from 4 042 singleton pregnant women were tested at 8-12+6,13-19+6,20-27+6,and 28-40 weeks of gestation and were used to establish the normal gestationalspecific reference values of thyroid function.Among 3 895 women having thyroid function tested at 8-19+6 weeks of gestation with negative thyroid antibodies,there were 93 cases of subclinical hyperthyroidism,91 cases of subclinical hypothyroidism (SCH),three cases of hyperthyroidism and 3 708 cases euthyroid.There were 1 118 women [1 607 euthyroid cases,17 cases of subclinical hypothyroidism (SCH) and 34 cases of subclinical hyperthyroidism] had thyroid function retested at 20-27+6 and 28-40 weeks of gestation,and without medicinal intervention.Analysis of variance and LSD test were used to analyze the changes of maternal thyroid function.Results (1) The reference ranges of TSH at 8-12+6,13-19+6,20 27+6 and 28-40 weeks of gestation [median (Pz5-P97.5)] were 1.32 (0.03-4.17),1.83 (0.19-4.94),2.27 (0.70-5.42) and 2.34 (0.63-5.52) mU/L respectively.(2) Without medicinal intervention,thyroid function became normal in 80％ (45/56) SCH women at 20-27+6 weeks,but 20％ (9/45) of them developed SCH again at 28-40 weeks.The thyroid function became normal in 75％ (70/93) women with subclinical hyperthyroidism at 20-27+6 weeks,but in 15％ (14/93) of them,thyroid function remained abnormal at 28-40 weeks.9.40％ (30/319) and 6.25％ (21/336) euthyroid women with TSH ≥ 3 mU/L at 8-19+6 weeks of gestation developed SCH at 20-27+6 weeks and 28-40 weeks,while 0.42％ (5/1 202) and 0.86％ (10/1 163) euthyroid women with TSH ＜3 mU/L had SCH.1.66％ (20/1 202) and 1.98％ (23/1 163) euthyroid women with TSH＜3 mU/L at 8-19+6 weeks of gestation developed subclinical hyperthyroidism at 20-27+6 weeks and 28-40 weeks of gestation.(3) In comparison between 8-19+6 weeks and 20-27+6 weeks of gestation,TSH levels increased by (0.47±0.03) mU/L in euthyroid women,and more significantly in subclinical hyperthyroidism women [(0.82±0.06) mU/L],but decreased by (1.67±0.25) mU/L in SCH women (LSD test,all P＜0.05).The FT3 levels decreased by (0.47±0.02) pmol/L in euthyroid women,and more significantly in subclinical hyperthyroidism and SCH groups [(1.02± 0.18) and (0.72±0.08) pmol/L,LSD test,all P＜0.05].FT4 decreased by (2.31 ±0.04) pmol/L in euthyroid women,and more significanly in subclinical hyperthyroidism women [(4.63± 0.62) pmol/L] (LSD test,P＜0.05),but the decrement in SCH group [(1.78±0.28) pmol/L] was similar to euthyroid women (LSD test,P＞0.05).There were no significant differences in changes of TSH,FT3 and FT4 at 20-27+6 weeks and 28-40 weeks among euthyroid women,SCH and subclinical hyperthyroidism groups (F=1.01,1.14 and 2.04,all P＞0.05).Conclusions Women with subclinical thyroid dysfunction with negative thyroid antibodies experience significantly different natural changes when compared with euthyroid women,especially before 28 weeks of gestation.
Key words:
Pregnancy complications; Hypothyroidism; Hyperthyroidism; Thyrotropin; Triiodothyronine; Thyroxine; Reference values
Subclinical infection
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BACKGROUND:Obesity can influence thyroid function through multiple routes, even in people who are euthyroid. The correlation between weight and thyroid function is a matter of debate. The present study investigated the relationship between body weight and thyroid function in euthyroid Chinese adults. MATERIAL AND METHODS:A total of 1564 participants with serum thyrotropin (TSH) and thyroid hormone levels within the reference range were included. All of them were tested for thyroid function parameters and categorized, based on body mass index (BMI), into 3 groups: normal weight, overweight, and obese. The effects of BMI on thyroid function were examined using linear (continuous values) and logistic (dichotomous levels according to medians or means) regression and controlling for age and sex. RESULTS:There were significant differences in free triiodothyronine (FT3) levels and FT3/free thyroxine (FT4) ratios among participants who were normal weight, overweight, and obese (both P<0.001). Multivariable regression analysis (P<0.001) showed that BMI was positively associated with FT3 levels and FT3/FT4 ratios. Compared with the normal weight group, the patients who were overweight or obese had significantly higher FT3 levels and FT3/FT4 ratios that were higher than average, according to logistic regression analyses. CONCLUSIONS:We found that Chinese adults who are obese may have higher FT3 levels and FT3/FT4 ratios than those who are of normal weight, even if their thyroid function values are within the normal range.
Free thyroxine
Reference range
Thyroid-stimulating hormone
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This paper described the changes in the levels of serum triiodothyronine, serum thyroxine,serum thyrotrophin and other indices of thyroid function between 2-5 y after completion of antithyroid drug therapy in 35 patients who were euthyroid on clinical criteria. There was a small but significant elevation of the mean triiodothyronine and thyroxine levels with a relative hypersecretion of Triiodothyronine. No correlation was found between the levels of either thyroid hormone measured or their ratio and the radioiodine uptakes and clearance rate, the plasma inorganic iodine level, the absolute iodine uptake or the serum TSH level. There was no case of clinical hypothyroidism but in one patient the TSH level was at the upper limit of the nrmal range and an exaggerated TSH response to TRH was found.
Wolff–Chaikoff effect
Free thyroxine
Thyroid-stimulating hormone
Reverse triiodothyronine
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Although the effects of hypothyroidism and hyperthyroidism on body weight have been clearly demonstrated, there is no sufficient data on the relationship between the body mass index (BMI) and minor differences within the normal range of thyroid function. The present study aims to investigate the relationship of fluctuations of the thyroid stimulating hormone (TSH) and thyroid hormones with BMI in euthyroid subjects. The study included 736 euthyroid healthy individuals of known age, weight, height, and biochemical picture of the thyroid function. Individuals were classified according to BMI and thyroid hormones’ values. The variations of normal thyroid function in euthyroid individuals were associated with body weight changes. A statistically significant positive correlation between BMI and thyroid function in women was found, while in men the correlation was not statistically significant. The alterations in thyroid function are mainly primary, while changes in body weight are secondary. The reason may be simple or multifactorial, and the biological mechanism is not completely known. Finally, the thyroid function disorders in conjunction with the strong influence of various environmental factors can increase body weight and lead to obesity.
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This is a retrospective study of 112 patients with GDM. The purpose is to evaluate the relationship between GDM and impaired thyroid function. All the patients were evaluated: TSH, FT4 and glycosylated hemoglobin (HbA1c). The normal range for TSH is between 0,45 and 2,5 μU/ml; for FT4 is instead between 0,9 and 1,8 ng/dl; for HbA1c is less than 6%. Patients with elevated TSH and low levels of free thyroxine were diagnosed as those with elevated TSH and FT4 in the standard as pregnant women who had high TSH and low FT4 were diagnosed as hyperthyroid; women with low TSH and normal FT4 as hyperthyroid. Patients who had normal levels of both thyrotropin and free thyroxine were considered euthyroid. Based on the values of TSH and FT4 we obtained the following results: 77 patients (68.75%) euthyroid; 18 (16.1%) subclinical hypothyroidism; 12 (10.7%) hypothyroid; 5 patients (4.4%) subclinical hyperthyroidism. Our study confirms the association between thyroid disease and gestational diabetes. In addition, the hypothyroid patients insulin-treated, compared with euthyroid, increased the insulin requirement. The results show that women with GDM have a risk greater for both clinical and subclinical hypothyroidism; for this reason it is advisable to carry out a program of screening for thyroid function.
Subclinical infection
Free thyroxine
Thyroid disease
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Methimazole
Wolff–Chaikoff effect
Antithyroid agent
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Objective: To observe the effect of different iodine intake on the thyroid function in euthyroid adult persons. Methods: One hundred and sixty-one euthyroid healthy volunteers aged 18-24 years were randomly divided into 7 groups. Each group was assigned to receive 500 μg, 750 μg, 1 000 μg, 1 250 μg, 1 500 μg, and 2 000 μg iodide/day for four weeks. Serum concentrations of free triiodothyronine(FT3), free thyroxin(FT4) and sensitive thyroid-stimulating hormone (sTSH) were measured by chemoluminescence assays. Results: Serum FT3 concentration was found a small decline within the normal range in all the iodide supplemented groups (P 0.05). The level of FT4 was significantly lower, when the dose was up to 1 500 μg (P 0.05). The level of serum sTSH was increased after 2 weeks iodide supplement in all groups, and after 4 weeks in 500 μg and 750 μg groups(P 0.05). No significant changes were observed in FT3,FT4 and sTSH between groups(P 0.05). Conclu- sion: The thyroid function of normal people showed a rise in serum sTSH at a short time and a high-dose of iodine intake.
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Free thyroxine
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