We have studied the relationship between mean pretreatment levels of serum prolactin and the presence of positive immunohistochemical staining for prolactin in the pituitary tumours of 55 patients. Pretreatment serum prolactin was significantly higher in patients with tumours showing many prolactin immunostaining cells than in those with none (P less than 0.001). When the pretreatment serum prolactin exceeded 6000 mU/l, the tumours contained over 90% of prolactin positive cells; one patient was an exception who had received long-term high dose bromocriptine therapy, and her tumour showed only occasional cells with positive staining. When the pretreatment serum prolactin level was under 2500 mU/l, a tumour was found which showed either no cells or fewer than 1% of cells which stained for prolactin. There was no significant difference in pretreatment serum prolactin levels between 11 patients with craniopharyngiomas and 34 patients with pituitary macroadenomas showing no prolactin immunostaining. Seventy-one percent (32) of the 45 patients with craniopharyngiomas or tumours with negative immunostaining for prolactin, had raised pretreatment serum prolactin levels (above 360 mU/l) although this was usually only slightly elevated; the levels exceeded 2500 mU/l in six (13%) of them (two craniopharyngiomas, four pituitary tumours) but in none did the levels exceed 6000 mU/l. Four of the 55 pituitary tumours showed occasional cells (less than 1%) that stained positively for growth hormone. In none of the patients with these tumours was there evidence of acromegaly or pathologically elevated circulating growth hormone levels.

The clinical activity of the new ergoline, mesulergine, was compared to pergolide in the treatment of hyperprolactinaemia. Mesulergine was given to 22 women and five men with hyperprolactinaemia. Serum prolactin was substantially lowered in 10 women; two subsequently conceived and completed normal pregnancies. Twelve women stopped treatment due to side-effects, usually nausea and vomiting, or inadequate responses. The side-effects were generally similar to those on bromocriptine; in one patient they were better and in four worse than on bromocriptine. The male patients were more tolerant of mesulergine, and substantial falls in serum prolactin were seen with evidence of tumour shrinkage. Twenty-seven women with hyperprolactinaemia received pergolide; serum prolactin was lowered or normalized in 16. Side-effects necessitating cessation of treatment were similar to those seen with bromocriptine. Nevertheless, four women tolerated pergolide better than bromocriptine and two women adequately treated with mesulergine had previously been intolerant of pergolide. We conclude that both pergolide and mesulergine may be useful and effective drugs in the treatment of hyperprolactinaemia as alternatives to bromocriptine.