Effect of stilboesterol therapy on thyrotrophin-releasing hormone (TRH) responsiveness in males

The effects of drugs on tests of thyroid function

Many drugs affect tests of thyroid function through alterations in the synthesis, transport and metabolism of thyroid hormones, as well as via influences on thyrotrophin (TSH) synthesis and secretion. Despite effects on circulating thyroid hormone and TSH levels, few drugs result in important changes in clinical thyroid state, but difficulty in interpretation of thyroid function tests often results. Commonly prescribed drugs including anti-convulsants, non-steroidal anti-inflammatory drugs, beta-adrenoceptor antagonists, steroid hormones and heparin may result in abnormal thyroid function tests in the absence of clinical features of thyroid dysfunction. In contrast, lithium and iodine containing drugs, including radiographic contrast agents and amiodarone, may result rarely in overt thyroid disease.

Estrogenic treatment does not modify the TSH and PRL responses to domperidone and TRH in patients with tumoral hyperprolactinemia

To verify if the low estrogen regimen could condition the TSH hyperresponsivity and PRL hyporesponsivity to antidopaminergic drugs seen by us and others in patients bearing prolactinoma, the effect of ethynilestradiol treatment (50 micrograms/day/14 days) on TSH and PRL responses to domperidone in 6 women with tumoral hyperprolactinemia and hypoestrogenemia were studied. Estrogenic treatment was unable to modify the TSH and PRL responsiveness either to domperidone and TRH. These data do not support the hypothesis that hypoestrogenemia could cause the peculiar TSH and PRL pattern in response to antidopaminergic drugs, in patients bearing prolactinoma. Also the TRH releasable pool of TSH and PRL in these patients seems to be unaffected by estrogenic treatment.

TSH secretion in thalassemia

Thyroid function has been evaluated in 6 prepubertal male and 9 female thalassemic patients. Four of the latter were sexually immature (Group I), with very low estradiol levels and the remainder had more advanced sexual development (Group II). Subjects were challenged with TRH and the response compared to adult controls and a group of 15 males aged 13-18 years with constitutional delayed adolescence. All patient groups and controls had normal levels of T4, T3 and T3 resin uptake. When compared to adult controls or males with constitutional delayed adolescence, the male thalassemic patients had increased basal TSH levels with an exaggerated response to TRH. Long term testosterone enanthate led to a decrease in integrated TSH secretion, showing that androgens may decrease the TSH response to TRH. The more sexually mature females of Group II also had increased basal and stimulated TSH levels; however, the sexually immature females of Group I had basal TSH and TSH responses to TRH equivalent to female controls. In Group I patients there were, moreover, no changes in TSH response during administration of estradiol valearate for 3 months and conjugated estrogens for 8 months. The high basal and stimulated TSH levels in the males and Group II females are most likely due to subclinical primary hypothyroidism. This has been previously described in thalassemia. On the other hand, failure of estrogens to increase the TSH response to TRH in Group I females is evidence of pituitary involvement, which is also well documented in this clinical condition.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of thyrotrophin releasing hormone in the diagnosis of isolated gonadotrophin deficiency

We studied the response of PRL and TSH to thyrotrophin-releasing hormone (TRH) in 15 boys with delayed adolescence and 6 male subjects with isolated gonadotrophin deficiency (IGD). TRH tests were repeated in the IGD subjects during and 1 month following hCG treatment. Male IGD subjects showed a significantly decreased basal and TRH induced PRL response compared to male controls and subjects with delayed adolescence. Human chorionic gonadotrophin (HCG) treatment of male IGD subjects restored basal and stimulated PRL levels to the range of normal controls. This was, presumably, an estrogenic effect since non aromatizable androgens did not increase the PRL response; moreover, the antioestrogen, clomiphene, decreased the PRL response when given with HCG. The TSH response to TRH in delayed adolescents was increased as compared to adult male controls and IGD subjects and was similar to adult female controls. HCG treatment of IGD subjects had no effect on basal nor peak TSH levels, although ethinyl oestradiol did increase the TSH response in two IGD subjects. These studies show that the PRL and TSH responses to TRH may differentiate delayed adolescence from IGD. The increased TSH response to TRH in delayed adolescence as compared to adult males, is a manifestation of an enhanced oestrogen effect in these patients. The abnormal PRL dynamics in IGD is a consequence of estrogen deficiency.

Clomiphene citrate does not modify the exaggerated thyrotrophin response to thyrotrophin-releasing hormone occurring in primary testicular failure

Patients with primary testicular failure have increased basal TSH levels and an exaggerated TSH response to TRH in the presence of normal circulating levels of thyroid hormones. In order to evaluate it this TSH profile is an oestrogen-related phenomenon, sixteen patients with primary testicular failure were challenged with 200 micrograms TRH prior to and after the administration of clomiphene citrate. The latter was given in a dose of 100 mg/day for 4 weeks to ten patients; 200 mg/day for 4 weeks to three patients and 100 mg/day for 2 months to the final three patients. The patients demonstrated increased mean basal TSH levels with an exaggerated TSH response to TRH. Following the administration of clomiphene citrate, there were no changes in T4, T3 sephadex or total T3 levels and in basal or stimulated TSH levels. Clomiphene did produce an increase in oestradiol, testosterone, basal gonadotrophins and LH response to LHRH. Since the oestrogen antagonist, clomiphene citrate, had no effect on TSH secretion, it is unlikely that the exaggerated TSH response to TRH is mediated by oestrogens.

Pharmacological interference with in vitro tests of thyroid function

Numerous drugs may cause changes in the serum concentrations of T4 and of T3. If such alterations are not recognized an incorrect diagnosis may result. In moderate degrees of hypo- and hyperthyroidism thyroid hormone levels may be spuriously normal, or the influence of pharmacological substances may lead to false diagnosis of thyroid disease in euthyroid patients. Since prediction of such alterations remains uncertain, it may be necessary to perform additional investigations when a potential artefact is recognized. On the other hand many pharmacological agents, especially those which interact with neurotransmitters, may influence TSH secretion, too. The TRH-test may show an increase or decreased TSH response, although complete suppression is only rarely seen during high-dose glucocorticoid treatment when low TRH doses are applied. Because of TRH-test gives such wide separation between different clinical states false interpretations are generally less likely than with drug-induced changes in T4 and T3 values.