Fig. 1.14 
Effect of TRH on prolactin and GH release in normal subjects and in patients with pituitary tumours. 
(a) TRH stimulates the release of prolactin in a normal subject, while having no effect in a patient with prolactinoma (the usual response in such patients). (b) TRH has no effect on plasma GH levels in a normal individual, while it stimulates GH release in a patient with acromegaly.