The measurement of the serum sex-hormone binding globulin in various thyroid diseases

Synthesis of "sex-hormone binding globulin" (SHBG) is influenced by thyroid hormones and its concentration in the serum of female subjects may be a marker of thyroid hormone effect at the peripheral tissue (liver) level. Compared to the levels found in euthyroid females (n = 46), the mean (+/- S.D.) serum SHBG concentration was found elevated in overt hyperthyroidism (Graves' disease: n = 56; 141.6 +/- 37.6 vs. 48.3 +/- 16.2; toxic nodular goiter: n = 16; 119.9 +/- 50.7 vs. 48.3 +/- 16.2 nmol/l; P less than 0.001). In contrast, it was decreased in manifest hypothyroidism (n = 25; 24.9 +/- 14.8 vs. 48.3 +/- 16.2; P less than 0.001). In the group of preclinical hyperthyroidism (n = 43), despite suppressed TSH secretion, the serum value of SHBG was normal (47.4 +/- 16.8), while its serum level approached the lower border of the normal range in subclinical hypothyroidism (n = 10; 33.6 +/- 6.1 vs 48.3 +/- 16.2 nmol/l; P less than 0.01). Data indicate that the pituitary responds more sensitively than the liver to a slight change of the serum thyroid hormone level. During thyroid hormone replacement for hypothyroidism, measurement of serum SHBG may provide help to assess the response of the target organ to the given therapy. In patients with generalized resistance to thyroid hormone, the serum SHBG level is within the normal range (51.3 +/- 9.8 nmol/l), thus, its determination supports the diagnosis of this disease.     

Exaggerated and prolonged thyrotrophin releasing hormone (TRH) test responses in tertiary hypothyroidism.

A 60 year old man with panhypopituitarism due to a large meningioma and prolonged and exaggerated thyroid stimulating hormone (TSH) responses is described. Initial investigations showed a subnormal urinary free cortisol concentration, a low serum cortisol taken at 0900 hours, and a low free T4 concentration. The TSH was towards the upper end of the normal range. Subsequently pituitary function tests showed subnormal production of luteinising hormone in response to luteinising hormone releasing hormone (LHRH) and a short synacthen test with a low 30 minute cortisol value. Long synacthen testing showed a normal response at four days, confirming that the abnormalities were due to a pituitary or hypothalamic cause. A computed tomogram showed a large meningioma compressing the hypothalamus, pituitary, and temporal lobe. TRH testing showed a prolonged and exaggerated response, consistent with tertiary hypothyroidism.     

甲状腺疾病与血清骨钙素的关系及其临床意义

观察各种甲状腺疾病治疗前、后血清骨钙素的变化，以探讨甲状腺功能异常与骨代谢的关系。本文对236例甲状腺疾病患者及52名健康志愿者为对照组，采用酶放大化学发光法测定了血清骨钙素(BGP)、FT3、FT4、TSH和人甲状腺球蛋白(HTG)。结果显示：正常人血清骨钙素水平随着年龄的增高而逐渐降低；甲亢患者治疗前。BGP浓度明显升高；甲减患者治疗前BGP浓度明显低于正常，经短期甲状腺紊替代治疗后，BGP浓度明显高于正常；治疗前的亚甲炎患者BGP浓度明显高于对照组，用糖皮质激素治疗后，BGP浓度反低于正常水平。相关统计表明，治疗前、后的甲亢、甲减和亚甲炎患者BGP与FT3、FT4之间呈明显的正相关；甲减患者BGP与TSH呈负相关。实验结果显示甲状腺激素可能直接参与加速骨转换过程，并以增加骨吸收过程为显著；糖皮质激素可使骨转换率减低，骨的形成降低，最终都可能导致骨矿丢失。     

In vitro TSH and PRL secretion from eutopic and heterotopic rat pituitaries: effects of hypothyroidism

Five adenohypophyses from donors of the same strain, age, and sex were transplanted under the renal capsule of young adult female rats. At least 3 wk later, enzymatically dispersed cells from eutopic or heterotopic adenohypophyses from the same rat were perifused in vitro in a small chamber. Thyrotropin (TSH) and prolactin (PRL) secretion per 10(6) cells were significantly less from heterotopic than from eutopic cells under all conditions. In cells from euthyroid animals, TRH induced TSH secretion only in the eutopic cells but induced PRL secretion in both eutopic and heterotopic cells. Hypothyroidism increased TRH-induced TSH secretion and content in the cell lysate in both eutopic and heterotopic cells but increased TRH-induced PRL secretion only in the eutopic cells. The increase in TSH secretion induced by hypothyroidism in the heterotopic cells was of borderline statistical significance. The inability of TRH to induce TSH secretion in heterotopic pituitary cells from euthyroid rats may be due to a lower set point for thyroid hormone inhibition of TSH secretion in the heterotopic thyrotrophs. Heterotopic pituitary TSH secretion is probably suppressed by the normal plasma thyroid hormone concentration maintained by the eutopic pituitary and may be stimulated by TRH only in the presence of a subnormal plasma thyroid hormone concentration.     

Examination of serum thyrotropic hormone level by 'supersensitive' immunoradiometric assay in functioning thyroid adenoma

TSH determination by immunoradiometric assay (IRMA) has enabled the detection of subnormal levels of TSH and has thus opened up new vistas in the differentiation between euthyroidism and hyperthyroidism. The present investigations have proved that in patients with autonomous functioning thyroid adenoma with progressive clinical trend, when 'non-toxic' nodular goitre transforms into toxic adenoma, the basal serum TSH level is gradually decreasing. In case of a functioning thyroid adenoma detected by scintigraphy, the basal TSH concentration of the serum over 0.3 mU/l indicates euthyroidism. In preclinical hyperthyroidism, similarly to toxic adenoma, the serum thyroid hormone determination contributes to differentiating between the two clinical states. The IRMA for TSH determination makes it unnecessary, in the majority of cases, to perform the TRH (thyreotrop-releasing hormone) loading-test, which is needed only if the basal serum TSH level is in the borderline range, i.e. between 0.1 and 0.3 mU/l.     

Effects of growth hormone treatment on thyroid function in pediatric patients with Prader–Willi syndrome

It is unclear whether hypothyroidism is present in patients with Prader–Willi syndrome (PWS). This study aimed to clarify the state of the hypothalamic–pituitary–thyroid axis and the effects of growth hormone (GH) treatment on thyroid function in pediatric patients with PWS. We retrospectively evaluated thyroid function in 51 patients with PWS before GH treatment using a thyroid‐releasing hormone (TRH) stimulation test (29 males and 22 females; median age, 22 months). We also evaluated the effect of GH therapy on thyroid function by comparing serum free triiodothyronine (fT3), free thyroxine (fT4), and thyroid stimulating hormone (TSH) levels at baseline, 1 year, and 2 years after GH therapy. TSH, fT4, and fT3 levels were 2.28 μU/ml (interquartile range [IQR]; 1.19–3.61), 1.18 ng/dl (IQR; 1.02–1.24), and 4.02 pg/dl (IQR; 3.54–4.40) at baseline, respectively. In 49 of 51 patients, the TSH response to TRH administration showed a physiologically normal pattern; in two patients (4.0%), the pattern suggested hypothalamic hypothyroidism (delayed and prolonged TSH peak after TRH administration). TSH, fT4, and fT3 levels did not change significantly during 1 or 2 years after GH treatment. The TSH response to TRH showed a normal pattern in most patients, and thyroid function did not change significantly during the 2 years after initiating GH treatment.     

Appropriate replacement dose of thyroxine in primary hypothyroidism

An ultrasensitive thyrotropin (TSH) assay was used to determine how many of 65 patients with primary hypothyroidism on thyroxine (T4) replacement therapy had suppressed serum TSH. In 13 patients (20%) TSH levels less than or equal to 0.1 mIU/l were found, indicating an overdose of thyroxine. After correction of the dose, 48 patients had normal TSH values. Their mean dose of thyroxine was 119 micrograms/24 hours, and the appropriate replacement dose tended to decline with advancing age. The serum level of thyroid hormones during replacement therapy with thyroxine very imperfectly reflected serum TSH values. It is concluded that overdose of thyroxine is common when suppressed serum TSH is used as an end point. Biochemical follow-up of replacement therapy with thyroxine in primary hypothyroidism therefore requires the use of an ultrasensitive TSH assay in order to detect such suppression. Serum levels of thyroxine or triiodothyronine (T3) during thyroxine therapy are poor indicators of pituitary TSH secretion and are therefore not useful as parameters of adequate thyroxine dosage.     

Effect of domperidone on serum TSH and growth hormone in thyroid patients

In euthyroid female patients, the release of TSH from the pituitary increases in response to domperidone, a dopaminergic-receptor blocking agent of peripheral action. The rate of increase varies with the functional state of the thyroid, as confirmed by results obtained in cases of euthyroidism, primary hypothyroidism, subclinical hypothyroidism and subclinical hyperthyroidism. Observations suggest that the more vigorous feedback-mechanism modulates the dopaminergic regulation of TSH-secretion at a high degree of sensitivity. Stimulation with 1-dopa intensifies the release of growth hormone from the pituitary which is, however, of lesser degree in hyperthyroid or hypothyroid than in euthyroid individuals. The GH-response to 1-dopa is enhanced by administration of propranolol, but the maximum serum GH levels in response to stimulation with 1-dopa are significantly lower in hyperthyroid than in euthyroid individuals. Administration of domperidone leaves the serum GH levels unaffected in euthyroid and hyperthyroid subjects, but causes a significant increase in a number of patients with primary hypothyroidism. The results suggest that the dopaminergic system plays a part in the regulation of TSH and GH secretion, asserting itself partly as a direct effect on the pituitary, and that the dopaminergic regulation may be affected by thyroid dysfunction.     

Increased need for thyroxine during pregnancy in women with primary hypothyroidism

BACKGROUND AND METHODS. Women with hypothyroidism have been thought not to require an increase in thyroxine replacement during pregnancy. To evaluate the effects of pregnancy on thyroxine requirements, we retrospectively reviewed the thyroid function of 12 women receiving treatment for primary hypothyroidism before, during, and after pregnancy. RESULTS. In all patients, the serum thyrotropin level increased during pregnancy. The mean (+/- SE) serum free-thyroxine index decreased from 111.0 +/- 5.8 before pregnancy to 86.5 +/- 5.2 during pregnancy (normal, 64 to 142; P less than 0.05), and the mean serum thyrotropin level increased from 2.0 +/- 0.5 mU per liter before pregnancy to 13.5 +/- 3.3 mU per liter during pregnancy (normal, 0.5 to 5.0 mU per liter; P less than 0.01). Because of high thyrotropin levels, the thyroxine dose was increased in 9 of the 12 patients. Among the three patients who did not require an increased thyroxine dose were two with low serum thyrotropin levels before pregnancy, suggesting excessive replacement at that time. The mean thyroxine dose before pregnancy was 0.102 +/- 0.009 mg per day; it was increased to 0.148 +/- 0.015 mg per day during pregnancy (P less than 0.01). The mean postpartum serum free-thyroxine index was 136.6 +/- 11.4 (P less than 0.05 as compared with values before and during pregnancy), and the mean postpartum serum thyrotropin level was 1.4 +/- 0.4 mU per liter (P less than 0.01 as compared with levels during pregnancy), demonstrating a decrease in the thyroxine requirement. The mean postpartum thyroxine dose was decreased to 0.117 +/- 0.011 mg per day (P less than 0.01 as compared with the dose during pregnancy). CONCLUSIONS. Our results indicate that the need for thyroxine increases in many women with primary hypothyroidism when they are pregnant, as reflected by an increase in serum thyrotropin concentrations. Although the effects of this modest level of hypothyroidism are not known, we think it prudent to monitor thyroid function throughout gestation and after delivery and to adjust the thyroxine dose to maintain a normal serum thyrotropin level.     

A case report of idiopathic myxedema with secondary amenorrhoea and hyperprolactinemia: effect of thyroid hormone replacement on reduction of pituitary enlargement and restoration of fertility

A 37-year old housewife was admitted to our department because of long-standing amenorrhoea and galactorrhoea. After several hormonal examinations, she was proved to be suffered from primary hypothyroidism with hyperprolactinemia. In addition, brain computed tomography (CT) showed the finding of enhanced pituitary enlargement, suggesting pituitary hypertrophy or pituitary adenoma. Based on some therapeutic experiences in similar cases in several reports, we have performed only thyroid hormone replacement and followed up the patient. Plasma thyroid stimulating hormone (TSH) and prolactin concentrations returned to normal range in a few months after starting thyroid hormone replacement. Furthermore, the finding of pituitary enlargement has completely disappeared on brain CT and come to pregnancy during the course. Thus, it seems that the finding of pituitary enlargement might be due to pituitary hypertrophy. Therefore, we think that thyroid hormone replacement should be a first choice therapy preceding the pituitary surgery or bromocriptine therapy in such a case.     

血清TSH和Hcy测定在甲状腺功能减退诊断中的价值

目的 分析血清甲状腺激素（TH）和同型半胱氨酸（Hcy）水平测定在甲状腺功能减退诊断中的价值。方法 选取2018年2月~2019年2月在我院诊治的50例甲状腺功能减退患者设为观察组A,40例亚临床甲状腺功能减退患者设为观察组B,另选同期体检正常者40例设为对照组。分别检测三组TH[三碘甲状腺原氨酸（T3）、甲状腺素（T4）、促甲状腺素（TSH）]、Hcy水平并进行比较。结果 观察组B血清FT3、FT4水平与对照组比较,差异无统计学意义（P＞0.05）,血清TSH、Hcy水平高于对照组（P＜0.05）;观察组A血清FT3、FT4水平低于对照组,血清TSH、Hcy水平高于对照组（P＜0.05）;观察组A血清FT3、FT4水平低于观察组B,血清TSH、Hcy水平高于观察组B（P＜0.05）;血清TSH、Hcy变化与临床甲状腺功能减退呈正相关（P＜0.05）;血清TSH、Hcy诊断甲状腺功能减退敏感度和特异度均高于FT3、FT4诊断（P＜0.05）。结论 动态监测血清TSH、Hcy 水平,对亚临床甲状腺功能减退向临床甲状腺功能减退转化具有一定的诊断价值。     

暂停甲状腺激素替代治疗对分化型甲状腺癌患者血脂的影响

目的：探讨分化型甲状腺癌（DTC）患者暂停左旋甲状腺素（优甲乐）替代治疗后血脂的变化。方法：分别检测55例接受131I放射性治疗的DTC患者在激素替代治疗期间和停药4周后甲状腺功能全套（全自动化学发光法）和血脂全套7项（生化法）（三酰甘油、胆固醇、低/高密度脂蛋白、载脂蛋白A、B和E）,并对结果进行相关性分析。结果：暂停激素替代治疗4周后,患者均出现程度不同的甲减表现,TSH水平（中位数及范围）由0.45（0.07-27.13）mIU/L上升到92.4（8.4〉150）mIU/L;血脂7项指标水平亦升高,除三酰甘油外,其余6项与TSH水平相关,有显著性（rs=0.453-0.601,P〈0.002）。结论：暂停甲状腺激素替代治疗4周后,甲状腺癌患者血脂水平普遍升高,表明脂代谢水平受到一定程度的抑制。     

Lipid profile in different degrees of hypothyroidism and effects of levothyroxine replacement in mild thyroid failure

The aim of this study was to evaluate the lipid profile of patients with different degrees of hypothyroidism and the effect of levothyroxine replacement in subclinical hypothyroidism (SH). Initially, a cross-sectional study was performed with 226 participants [SH = 133 participants, manifest hypothyroidism (MH) = 23 participants, and euthyroidism (EU) = 70 participants]. The mean levels of atherogenic lipid variables were greater in MH than in SH and were greater in SH than in EU, although the differences between SH and EU did not reach statistical significance. The SH subgroup with greater serum thyrotropin (TSH) levels and that with positive antithyroperoxidase antibodies (TPO-Ab) had greater levels of triglycerides and of the atherogenic index Apo B/Apo A. A positive correlation exists between serum TSH and total cholesterol (rs = 0.167; P = 0.006), triglycerides (rs = 0.219; P < 0.001), and ApoB levels (rs = 0.205; P < 0.001). Eleven patients who received levothyroxine (L-T4) treatment and 15 patients who received placebo were reevaluated 1 year after TSH adjusted intervention. A fall in atherogenic variables was observed in the L-T4-treated group, with significance for total cholesterol (-20.0 vs +16.1 mg/dL in the placebo group) and LDL-c (-21.7 vs +17.2 mg/dL). We concluded that SH leads to an intermediary lipid profile between euthyroid individuals and that found in manifest hypothyroidism and that a significant lipid profile improvement occurred 1 year after L-T4 replacement therapy.     

体检人群甲状腺激素水平调查

目的 调查体检人群甲状腺激素水平,为健康指导及防治甲状腺疾病提供帮助.方法 采用微粒子化学发光法检测体检人群TSH、FT3和FT4.结果 ①随着年龄的增长,各年龄组TSH平均浓度呈上升趋势,FT3平均浓度呈下降趋势;②各年龄组甲状腺激素异常检出率存在差异.其中男性随着年龄的增长甲状腺激素异常检出比例呈上升趋势,年龄与患病率成较高的相关性;③＞ 50岁的人群甲减和亚甲减的患病率显著高于≤50岁的人群,差异有统计学意义（P＜0.05）;④女性甲状腺疾病患病率高于男性,其中甲减、亚临床甲减和甲亢的患病率差异具有统计学意义（P＜0.01）.结论 除了61～ 70年龄组的女性人群出现偏离外,所有男性组和其余各年龄段女性组,随着年龄的增长甲状腺激素异常检出比例总体呈上升趋势.50岁以上人群尤其是女性是患甲状腺疾病的高危人群,且甲状腺疾病多以甲状腺功能减退症和亚临床甲状腺功能减退症为主.     

Hypothyroidism,new nodule formation and increase in nodule size in patients who have undergone hemithyroidectomy

Introduction

The current medical literature has conflicting results about factors related to hypothyroidism and nodular recurrences during follow-up of hemithyroidectomized patients. We aimed to evaluate factors that may have a role in new nodule formation, hypothyroidism, increase in thyroid lobe and increase in nodule volumes in these patients with and without Hashimoto''s thyroiditis (HT), and with and without levothyroxine (LT4) use.

Material and methods

We enrolled 140 patients from five different hospitals in Ankara and evaluated their thyroid tests, autoantibody titre results and ultrasonographic findings longitudinally between two visits with a minimum 6-month interval.

Results

In patients with HT there was no significant difference between the two visits but in patients without HT, thyroid stimulating hormone (TSH) levels and nodule volume were higher, and free T4 levels were lower in the second visit. Similarly, in patients with LT4 treatment there was no difference in TSH, free T4 levels, or lobe or nodule size between the two visits, but the patients without LT4 had free T4 levels lower in the second visit. Regression analysis revealed a relationship between first visit TSH levels and hypothyroidism during follow-up.

Conclusions

Patients who have undergone hemithyroidectomy without LT4 treatment and without HT diagnosis should be followed up more carefully for thyroid tests, new nodule formation and increase in nodule size. The TSH levels at the beginning of the follow-up may be helpful to estimate hypothyroidism in hemithyroidectomized patients.     

Thyroid function tests

About 80% of thyroid disease consists of thyroid-specific autoimmune diseases, Hashimoto's disease and Grave's disease. To diagnose thyroid diseases, testings for (1) thyroid function and (2) pathogenetic autoantibodies are indispensable. To assess thyroid function, serum hormone concentrations, such as TSH, FT4 and FT3 are measured. Among these hormones, serum TSH concentrations are the most reliable and informative regarding thyroid function, correcting indicating a hyperthyroid, euthyroid or hypothyroid state. Therefore, TSH measurement appears to be the first choice in selecting the hormone determination. Reference intervals for normal healthy subjects of TSH are around 0.4-5.0 microU/ml. The second choice for thyroid function assessment are FT4 which supersedes total T4(TT4). TT4 is affected by changes in serum thyroid hormone binding proteins(TBG, TTR, Albumin). For example, euthyroid pregnant women whose serum TBG are physiologically higher than those of non-pregnant women show augmentation of TT4. However, FT4 depicts within reference intervals, although measurement of FT4 alone is unable to detect any abnormality of thyroid hormone binding proteins. According to its plasma concentration and binding affinity, FT3 measurement deserves no more significance than T3. Another important test for thyroid diseases is to detect serum autoantibodies against thyroid tissues, such as TgAb, TPOAb. Much more important is TSH receptor antibody which differentiates Graves' disease from Hashimoto's thyroiditis. In patients who show hyperthyroidism and some very uncommon hypothyroidism, TSH receptor antibodies should be measured. Three indicators are available as routine tests; TRAb measured by radioreceptor assay; TSAb determined by bioassay using cultured porcine thyroid cells. Usually, TRAb activity clinically correlates well with TSAb. TSBAb was initially discovered in patients with severe hypothyroidism with atrophic thyroid gland. TSBAb blocks thyroid stimulating activity of TSH and consequently causes severe hypothyroidism. TRAb and TSAb are very useful to diagnose and follow patients with Grave's disease.     

The effect of iodine restriction on thyroid function in patients with hypothyroidism due to Hashimoto's thyroiditis

Lifelong thyroid hormone replacement is indicated in patients with hypothyroidism as a result of Hashimoto's thyroiditis. However, previous reports have shown that excess iodine induces hypothyroidism in Hashimoto's thyroiditis. This study investigated the effects of iodine restriction on the thyroid function and the predictable factors for recovery in patients with hypothyroidism due to Hashimoto's thyroiditis. The subject group consisted of 45 patients who had initially been diagnosed with hypothyroidism due to Hashimoto's thyroiditis. The subjects were divided randomly into two groups. One group was an iodine intake restriction group (group 1) (iodine intake: less than 100 micro g/day) and the other group was an iodine intake non-restriction group (group 2). The thyroid-related hormones and the urinary excretion of iodine were measured at the baseline state and after 3 months. After 3 months, a recovery to the euthyroid state was found in 78.3 % of group 1 (18 out of 23 patients), which is higher than the 45.5% from group 2 (10 out of 22 patients). In group 1, mean serum fT4 level (0.80 +/- 0.27 ng/dL at the baseline, 0.98 +/- 0.21 ng/dL after 3 months) and the TSH level (37.95 +/- 81.76 micro IU/mL at the baseline, 25.66 +/- 70.79 micro IU/mL after 3 months) changed significantly during this period (p < 0.05). In group 2, the mean serum fT4 level decreased (0.98 +/- 0.17 ng/dL at baseline, 0.92 +/- 0.28 ng/dL after 3 months, p < 0.05). In the iodine restriction group, the urinary iodine excretion values were higher in the recovered patients than in non-recovered patients (3.51 +/- 1.62 mg/L vs. 1.21 +/- 0.39 mg/ L, p=0.006) and the initial serum TSH values were lower in the recovered patients than in the non-recovered patients (14.28 +/- 12.63 micro IU/mL vs. 123.14 +/- 156.51 micro IU/mL, p=0.005). In conclusion, 78.3% of patients with hypothyroidism due to Hashimoto's thyroiditis regained an euthyroid state iodine restriction alone. Both a low initial serum TSH and a high initial urinary iodine concentration can be predictable factors for a recovery from hypothyroidism due to Hashimoto's thyroiditis after restricting their iodine intake.     

Hypothalamus-pituitary-thyroid axis interactions with pineal gland in the rat.

We examined in the rat several possible relationships between the pineal gland and the hypothalamus-pituitary-thyroid axis. The pineal gland, the retina, and the hypothalamus exhibited a diurnal rhythm in thyrotropin-releasing hormone (TRH) content with peak values occurring around 1200 h. This rhythm in the hypothalamus was abolished by constant light but was not affected by pinealectomy. Nor did pinealectomy affect hypothalamic TRH content, pituitary content of thyroid-stimulating hormone (TSH) or prolactin; serum levels of (TSH), triiodothyronine (T3), or thyroxine (T4), or serum free-thyroxine index; or free-triiodothyronine index. Melatonin did not affect TSH or prolactin release from the anterior pituitary or TRH release from the hypothalamus in vitro. Isoproterenol did not affect the TRH content of pineal glands in vitro; nor did TRH or T3 affect basal or stimulated activities of serotonin N-acetyltransferase, the presumed controlling enzyme in melatonin production. We found no evidence for significant interactions between the pineal gland and the hypothalamus-pituitary-thyroid axis.     

Effect of diphenylhydantoin on hypothalamic-pituitary-thyroid function in the rat

Chronic diphenylhydantoin (DPH) administration (5 mg x 100 g body wt-1 x day-1) to the normal rat is associated with a decrease in the serum thyroxine (T4) and triiodothyronine (T3) concentrations without an appropriate rise in the serum thyrotropin (TSH) concentration, suggesting a possible direct effect of DPH on TSH secretion. To further study this possibility, DPH was administered chronically to thyroidectomized, hypothyroid rats. In the hypothyroid rats treated chronically with DPH, serum TSH did not increase, pituitary TSH content was significantly decreased, and the serum TSH response to thyrotropin-releasing hormone (TRH) was decreased compared to that of diluent-treated, hypothyroid rats. Hypothalamic TRH content was similar in DPH and diluent-treated rats. These findings suggest that DPH suppresses pituitary TSH secretion, probably as a thyroid hormone agonist. The effect of a single large dose of DPH (20 mg/100 g body wt) administered to thyroidectomized rats also decreased serum tSH but, in contrast to the findings in chronically treated rats, hypothalamic TRH and pituitary TSH content and the serum TSH responses to TRH were increased. These differences may be due to the acute inhibitory effect of a large dose of DPH on hypothalamic TRH release. Furthermore, because the effect of thyroid hormone on regulating pituitary TSH synthesis and release is dose and time dependent, the effect of DPH as a thyroid hormone agonist on pituitary TSH dynamics may also be variable.     

老年慢性肺心病的甲状腺功能变化

本文用放免法测定了34例老年慢性肺心病患者的甲状腺激素水平,以探讨老年慢性肺心病人的甲状腺功能状态。结果发现,老年慢性肺心病组血清的TT_3、TT_4均值明显低于健康对照组(p<0.01),而TSH均值二者比较无明显差异。急性发作期组TT_3、TT_4明显下降,尤以TT_3明显,分别为1.04±0.37(nmol/L)和95.83±36.58(nmol/L),缓解期组T_3、T4_均有回升,分别为1.58±0.61(nmol/L)和105±26.66(nmol/L),说明肺心病T_3、T_4下降与肺心病的严重程度有关。急性发作期组TSH与缓解期组及健康人组比较则无明显差异,说明老年肺心病患者的甲状腺功能有一定程度减退。而TSH测定正常,能排除原发性甲状腺功能减退所致的T_3、T_4改变,符合低T_3综合征,提示下丘脑的保护性适应。动态观察血清T_3、T_4的变化,对于判断治疗和预后有一定的价值。