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

Abstract

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 estrogenie 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.