Functional Evaluation of Prolactin Secretion in Patients with Hypothalamic-Pituitary Disorders

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Abstract
Prolactin secretion was assessed in 23 patients with hypothalamic-pituitary disorders using L-Dopa suppression, chlorpromazine (CPZ), and thyrotropin-releasing hormone (TRH) stimulation tests. Based on the responses to these tests, three groups of patients were identified: those with panhypopituitarism (group I) and those with partial hypopituitarism either with (group II) or without (group III) evidence of hypothalamic involvement. Panhypopituitary patients (group I) consistently had low serum prolactin values and failed to respond to all tests. Patients with hypothalamic involvement (group II) exhibited (a) elevated basal prolactin values. (b) an increase in serum prolactin after TRH stimulation. (c) blunted response to L-Dopa, and (d) lack of response to chlorpromazine stimulation. Patients with partial hypopituitarism but without hypothalamic involvement (group III) had normal serum prolactin levels and suppressed normally after L-Dopa; although the magnitude of response to both stimulatory agents was significantly lower than normally found the ratio of prolactin levels post-CPZ and TRH (Δ prolactin CPZ/Δ prolactin TRH) was similar to the ratio of normal individuals suggesting that these patients (group III) had a normal hypothalamic-pituitary prolactin axis. In the 23 patients studied, the most consistent disorder of pituitary function proved to be an abnormal response to one or other of the three tests employed for the evaluation of prolactin secretion. Hence these tests have considerable potential as a sensitive screening procedure in the evaluation of patients suspected of having hypothalamic-pituitary disease.