OBJECTIVE To evaluate the various types of pituitary adenomas according to sex and age group. Few studies have attempted such an analysis, and most have focused on specific age groups, especially children. Recent data suggest that the frequency of different types of pituitary adenomas varies according to age and sex.

DESIGN A retrospective review of the records of 2230 patients who underwent surgery for a pituitary adenoma at the University of California, San Francisco (UCSF), between January 1969 and June 1993.

METHODS The distribution of tumours was analysed according to age at surgery, sex, and the clinical pheno‐type of the tumour. Age groups were defined as the decades of life.

RESULTS Prolactinomas were the most common tumours (39%), followed by endocrlne‐inactive adenomas, growth‐hormone‐releasing adenomas, and adrenocorficotrophic hormone‐releasing adenomas causing Cushing's disease; ACTH‐releasing adenomas causing Nelson's syndrome and thyrotrophin (TSH)‐releasing adenomas were rare. The female‐to‐male ratio differed considerably between the various adenoma types and between age groups. Prolactinomas, ACTH‐releasing adenomas, and TSH‐releasing adenomas occurred mostly in females; endocrine‐inactive and GH‐releasing adenomas occurred mostly in males. In older age groups, all adenoma types, except for endocrine‐inactive adenomas, tended to assume a more balanced gender distribution. Among patients with prolactinomas, endocrine‐inactive, ACTH‐releasing, and to a lesser extent GH‐releasing adenomas, the greatest discrepancy in gender distribution seemed to coincide with the peak Occurrence of each tumour type. The peak Occurrence was from the second to the fifth decade of life for prolactinomas and from the fourth to the eighth decade for endocrine‐inactlve adenomas. GH‐releasing, ACTH‐releasing, and TSH‐releaslng adenomas were more evenly distributed throughout the adult life span.

CONCLUSIONS The frequency of pitultary adenomas varies greatly according to age and sex. The various adenoma types have thelr peak occurrence in distinctly dlfferent age groups and differ greatly in their female‐to‐male ratios. The female‐to‐male ratio for a given adenoma type varies greatly with age.