Causes of Hyperprolactinemia in Acromegalic Patients and Clinical Correlations

Hyperprolactinemia in acromegalic patients may result either from cosecretion of growth hormone and prolactin by the tumour or from pituitary stalk compression. The occurrence of both conditions is possible. This study was designed aiming 1) to estimate the prevalence of each cause of hyperprolactinemia and its respective clinical course; 2) to compare the outcomes of patients with tumours staining only for growth hormone against tumours staining for both growth hormone and prolactin. 75 acromegalic patients submitted to transsphenoidal surgery between 1989 and 2018 were included. Patients were divided based on preoperative prolactin levels and immunostaining pattern. Statistical analysis was performed with SPSS version 23. Hyperprolactinemia was documented in 22 out of 36 patients (61%). Stalk compression was the only underlying cause of hyperprolactinemia in 45% of cases. The levels of prolactin were not associated with the immunostaining pattern for prolactin. Clinical differences were not observed between hyperprolactinemic and normoprolactinemic patients, except for a higher frequency of cavernous sinus invasion (64% vs 29%, p=0,064), that reached the level of significance for the subgroup with macroadenomas staining exclusively for growth hormone (p=0,031). In the present series, no clinical differences were noticed between patients with tumours staining only for growth hormone or staining for both growth hormone and prolactin. Hyperprolactinemia resulting from stalk compression is likely to anticipate a less favourable course of disease, since it is associated with larger tumours and a higher frequency of cavernous sinus invasion. On the contrary, positive immunostaining for prolactin was not a marker of worse prognosis.