Relationship between plasma prolactin concentration and pituitary function in patients with a pituitary adenoma

The influence of hyperprolactinaemia on endocrine functions in forty-two consecutive patients with untreated pituitary tumours was studied. Patients with acromegaly, Cushing's disease and Nelson's syndrome were excluded. Sixteen patients (eleven men and five women) had a pituitary adenoma with suprasellar extension and twenty-six (eleven men and fifteen women) had a small intrasellar tumour. Basal plasma prolactin concentration was measured in all. Thyroid function was assessed by plasma thyroxine (T4) and TSH concentrations, adrenocortical function and growth hormone (GH) secretion by the maximum plasma cortisol, adrenocorticotrophin (ACTH) and GH concentrations, respectively, during insulin-induced hypoglycaemia (tITT). Gonadal function was studied by measuring plasma concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), oestradiol-17 beta and in men, testosterone. On the basis of computer assisted tomography of the sella turcica, the tumour volume was calculated. The basal plasma prolactin concentration was elevated in 69% of the patients. Decreased GH secretion was the most frequent pituitary dysfunction (78%) followed in men by gonadal insufficiency (77%), adrenocortical insufficiency (31%) and thyroid insufficiency (21%). There was no difference between patients with elevated and normal plasma prolactin concentration as to the tumour volume and any of the endocrine variables.