The 24-hour profile of plasma prolactin in men with major endogenous depressive illness

Plasma prolactin (PRL) levels were measured at 15-minute intervals for 24 hours in 18 men suffering from major endogenous depressive illness and in 7 age-matched healthy men. Eleven of the 18 depressed patients were restudied during clinical remission following either electroconvulsive therapy or treatment with amitriptyline hydrochloride. During the acute phase of the illness, the unipolar depressed patients had fragmented patterns of PRL secretion with an early timing of the nocturnal secretory phase of PRL, which started, on the average, 2 hours earlier than in healthy subjects. Moreover, the amplitude of the circadian variation of PRL was reduced in these patients, with subnormal PRL levels occurring during the midsleep period. This latter abnormality was also observed in bipolar patients, who had otherwise normal PRL profiles. These lower midsleep PRL concentrations were associated with a significant increase in the amount of time spent awake during the same period. Antidepressant treatment did not consistently correct the abnormalities in the patterns of PRL release observed during the acute phase of the illness. These results indicate that early timing of nocturnal PRL secretion and damping of the nighttime PRL elevation may be found in men with endogenous depressive disorders. In contrast to disturbances of the corticotropic and somatotropic axes, these abnormalities of PRL secretion may still be present during clinical remission following antidepressant treatment.