A clinical study of the pineal hormone melatonin in patients with growth hormone or prolactin secreting pituitary tumours.

OBJECTIVES

Despite the well documented influence of the pineal gland on pituitary function, the evaluation of pineal activity is not generally included in the clinical investigation of patients with pituitary tumours. The present study analyzed the circadian secretion of melatonin, the main pineal hormone, in patients with pituitary adenomas.

METHODS

The study included 36 patients with pituitary tumours (acromegaly: 11; prolactinoma: 25), by comparing the results with those seen in 42 healthy controls. Moreover, patients were endocrinologically investigated after oral administration of 10 mg of melatonin.

RESULTS

Abnormally high serum levels of melatonin during the period of maximum light and abnormally low increases during the night were seen in 7/36 and 16/36 patients, respectively, without any relation to tumour histotype. Moreover, night serum mean levels of melatonin were significantly lower in patients than in controls. Finally, the exogenous administration of melatonin did not influence growth hormone and prolactin secretions in patients with acromegaly and prolactinomas, respectively.

CONCLUSION

This study demonstrates the existence of an altered pineal function in patients with pituitary tumours. Further studies will be required to establish the pathogenetic and prognostic significance of pineal disorders in neoplastic disease of the pituitary gland.