Plurihormonality of pituitary adenomas in light of immunohistochemical studies

Plurihormonality of pituitary adenomas can be defined as the ability of an adenoma to express more than one pituitary hormone. The application of immunohistochemistry to diagnose surgically removed pituitary tumours revealed that a great number of pituitary adenomas are in fact plurihormonal. However, data on the incidence and the clinical relevance of the pituitary adenoma plurihormonality are still scarce and controversial.

Hundred fifty-five pituitary adenomas, surgically removed, were studied immunohistochemically with the antibodies against pituitary hormones or their subunits. Additionally, 40 adenomas were immunostained with Ki-67 antibody to evaluate the proliferative potential.

According to the World Health Organization (WHO) recommendations, we did not consider tumours expressing both FSH and LH (gonadotropinomas) or somatoprolactinomas expressing both GH and prolactin as plurihormonal. Even with this limitation, plurihormonality was found to be a frequent finding in both hormonally active and clinically non-functioning pituitary adenomas. It was shown that over one-third (36.1%) of the investigated adenomas expressed more than one hormone. Plurihormonality, especially that which is connected with co-expression of ACTH, seems to be more frequent in the recurrent tumours. Plurihormonal adenomas also possess higher Ki-67 indices, as compared to monohormonal tumours.

Plurihormonality is a frequent phenomenon in both hormonally active and clinically non-functioning pituitary adenomas. It also seems to predict a higher risk of tumour recurrence. (Pol J Endocrinol 2010; 61 (1): 63-66).