In six patients suffering from amyotrophic lateral sclerosis we evaluated 
changes of T4, T3, TSH, PRL, and GH during treatment by continuous iv infusion 
of TRH for at least 15 days. No clinical improvement was detected. A significant 
rise of thyroid hormone levels was observed, as well as an upward trend of basal 
TSH levels and no change of basal PRL and GH levels. TRH acute test-induced TSH 
and PRL responses became blunted. Treatment provoked also the onset of a 
responsiveness of PRL to GHRH. The reduced TSH and PRL responses to acute TRH 
test during treatment could be explained by a down-regulation of TRH pituitary 
receptors. On the contrary, the onset of PRL responsiveness to GHRH is at 
present without a satisfactory explanation.