Klinefelter's Syndrome: Examination of Thyroid Function, and the TSH and PRL Responses to Thyrotropin-Releasing Hormone Prior to and after Testosterone Administration

Abstract

Thyroid function and prolactin (PRL) responsiveness to thyrotropin-releasing hormone (TRH) were examined in 6 patients with Klinefelter's syndrome prior to and after therapy with testosterone. The thyroid function tests, including serum triiodothyronine (T3), thyroxine (T4), thyroxine binding globulin (TBG), resin T3 uptake (RT3U), radioactive iodine uptake (RAIU), thyrotropin (TSH) stimulation and the TSH response to TRH were normal during both periods of study. Testosterone treatment had no significant effect on any of these parameters with the exception of the RT3U which increased. PRL response to TRH were significantly higher than those observed in normal men (P less than 0.05). Despite the fact that mean plasma PRL responses to TRH were decreased when the patients were restudied during testosterone therapy, they remained greater than those of normal men. Mean serum estradiol concentrations were normal and did not increase significantly during testosterone therapy. These studies suggest that: (1) thyroid function may be normal in patients with Klinefelter's syndrome more often than previously reported, and (2) patients with Klinefelter's syndrome may manifest PRL hyper-responsiveness to TRH that is decreased but not normalized during testosterone therapy. Because estradiol levels failed to increase despite a marked rise in testosterone, further studies are warranted to examine testosterone and estradiol clearance and conversion rates in patients with Klinefelter's syndrome.

Suppression of Testicular Androgenesis by <i>D</i>-Tryptophan-6-Luteinizing Hormone-Releasing Hormone Does Not Affect TSH Secretion in Male Subjects

“…In fact, when serum testosterone levels dropped to minimal val ues TSH secretion remained unchanged. These data are in keeping with those studies in which testosterone administration was un able to affect TSH secretion in patients with Klinefelter's syndrome [2], Conversely, there are also some reports in which, after testos terone administration to hypogonadal men, an increased [14] or blunted [11] pituitary response to TRH was observed. These dis crepancies may depend on different doses and pharmacological types of testosterone employed or on pretreatment testicular func tion of studied patients.…”

“…In fact, the lower TSH response to TRH in males can be ascribed either to low serum estrogen levels [5] or to high serum androgen levels [11]. Testosterone adminis tration inconsistently induces changes in the pituitary TSH response to TRH stimulation in hypogonadal male patients [2,11,14].…”

Should human chorionic gonadotropine treatment increase thyroid volume?

“…Additionally, Burman and cols. (14), showed that testosterone treatment had no significant effect on any of thyroid parameters in the patients with the Klinefelter's syndrome. On the contrary, Morley and cols.…”

“…Androgen replacement treatment (testosterone or gonadotropin treatment) have been used to in these patients (2). There was limited data about the effects of sex hormones and hCG on thyroid functions and thyroid volume among hypogonadal male patients (14,(16)(17)(18). Spitz and cols.…”

Effect of Non Aromatizable Androgens on LHRH and TRH Responses in Primary Testicular Failure

“…Increases in testosterone binding globulin (TeBG) have also been documented (Leroith et al 1981c). Several groups have assessed the effect of exogenous testosterone on PRL and TSH secretion in these patients (Burman, Dimond, Noel, Earll, Frantz and Wartofsky 1975;Cheikh, Hamilton, Hsu and Wiswell 1975;Smals, Kloppenborg, Lequin, Beex, Ross and Benraad 1977). In view of the fact that testosterone can be aromatized to estradiol or reduced to dihydrotestosterone (Nolin, Campbell, Nansel and Bogdanove 1977), the interpretation of these results is difficult because it is not possible to conclude which hormone is producing the effect.…”