Blunted prolactin response to thyrotropin-releasing hormone stimulation in cystinotic children receiving cysteamine.

We investigated whether long term cysteamine therapy in cystinotic children altered their basal and stimulated serum PRL levels. Five subjects who had normal plasma PRL responses to TRH stimulation before cysteamine treatment each had a lower basal PRL level and a blunted PRL response during long term (19-59 months) cysteamine therapy. A blunted PRL response was not found in 12 cystinotic subjects of the same age and stage of disease who had not received cysteamine. The effect on PRL release was not found in 2 subjects who received short term (1-2 weeks) treatment with full-dose cysteamine (50 mg/kg . day). The TSH response to TRH stimulation was not blunted during long term cysteamine therapy. These findings suggest that cysteamine alters PRL secretion in humans.