Secretion of neuron-specific enolase, prolactin, growth hormone, luteinising hormone and follicle stimulating hormone by "functionless" and endocrine-active pituitary tumours in vitro.

Secretion of the neuroendocrine marker neuron-specific enolase by 24 pituitary tumours was measured in maintenance tissue culture. Eleven endocrine-active and 13 "functionless" tumours were defined by measurement of prolactin, growth hormone, luteinising hormone (LH) and follicle stimulating hormone (FSH) secretion rates in vitro and the corresponding plasma hormone levels. Measurement of prolactin secretion provided a clear distinction between true prolactinomas and "functionless" tumours causing hyperprolactinaemia by stalk compression (pseudoprolactinomas). A previous report of LH and/or FSH secretion by the majority of "functionless" tumours was confirmed, but plasma levels of LH and FSH were usually normal. It is argued that LH and FSH are not the major hormones secreted by "functionless" tumours. A high production rate of neuron-specific enolase appears to be characteristic of the cell type from which most "functionless" tumours derive.