Prolactin Responsiveness to TRH and Metoclopramide in Thalassaemia

SUMMARY PRL and gonadotrophin secretion has been evaluated in six prepubertal male thalassaemic patients and nine females. Four of the latter were sexually immature (group 1) and the remainder had more advanced sexual development (group 2). Subjects were challenged with LHRH (100 μg), TRH (200 ug) as well as the dopaminergic antagonist, metoclopramide (10 mg) and their responses compared with normal adult controls. The male patients had low testosterone, oestradiol and basal and peak LH responses to LHRH. FSH values were intact. Basal PRL levels, as well as PRL responses to TRH and metodopramide were normal. There was a further increase in PRL response to TRH after the administration of a long acting testosterone preparation. In group 1 females, basal and peak gonadotrophins and oestradiol were decreased. Basal PRL was normal, but there was a markedly impaired PRL response to both TRH and metoclopramide. Oestradiol valerate administration restored the impaired PRL response to TRH, but not to metoclopramide in group 1 female subjects, although conjugated oestrogens had no effect. Group 2 females had normal gonadotrophin profiles, but low oestradiol levels. Their PRL response to TRH was normal, but they also demonstrated an impaired PRL response to metoclopramide. It is concluded that the impaired PRL reserve in female thalassaemic patients could be due to iron infiltration in the pituitary, or to oestradiol deficiency. It may also be related to the low LH levels or, alternatively, it may represent some alteration in dopamine tone.