Desai B, Burrin JM, Nott CA, Geddes JF, Lamb EJ, Aylwin SJB, Wood DF, Thakkar C, Monson JP. Glycoprotein hormone alpha-subunit production and plurihormonality in human corticotroph tumours—an in vitro and immunohistochemical study. Eur J Endocrinol 1995;133:25–32. ISSN 0804–4643
Glycoprotein hormone alpha-subunit (αSU) is a recognized product of clinically non-functioning, glycoprotein hormone-secreting and somatotroph adenomas but has not been studied systematically in corticotroph tumours. We have performed immunohistochemistry for αSU in a consecutive series of four corticotroph tumours causing Nelson's syndrome, three corticotroph macroadenomas, 12 corticotroph microadenomas and one adrenocorticotrophin-secreting bronchial carcinoid tumour. In addition we have assessed αSU secretion in vitro in corticotroph adenomas from two subjects with Cushing's disease and two subjects with Nelson's syndrome. Immunohistochemistry, performed after microwave treatment of sections to enhance antigen retrieval, demonstrated αSU positivity in 3/4 Nelson's tumours, 2/3 corticotroph macroadenomas, 7/12 microadenomas and one bronchial carcinoid. Eight of the 13 tumours positive for αSU were also immunostained after microwave pretreatment of sections for thyrotrophin (six positive), follicle-stimulating hormone (four positive), luteinizing hormone (three positive), β-chorionic gonadotrophin (five positive), growth hormone (three positive) and prolactin (two positive) immunoreactivity. In vitro cell cultures of all four tumours studied secreted adrenocorticotrophin and three secreted αSU, with the variable presence of luteinizing hormone, follicle-stimulating hormone, thyrotrophin, growth hormone and prolactin, in basal culture. The αSU secretion was augmented by phorbol ester (160 ± 15%, sem, n = 3 wells; p < 0.01) and 8-bromo-cAMP (138 ± 8%; p < 0.05) in one tumour. These data indicate that plurihormonality and, in particular, αSU elaboration and secretion by corticotroph tumours is more common than hitherto recognized. Possible mechanisms include abnormal or deregulated gene expression, autocrine or paracrine effects or a stem cell origin of tumour. The possible relationship of αSU production to corticotroph tumour behaviour and prognosis remains to be established.
John P Monson, Dept of Endocrinology, Royal London Hospital, Whitechapel, London El 1BB, UK
Secretion of neuron-specific enolase, prolactin, growth hormone, luteinising hormone and follicle stimulating hormone by "functionless" and endocrine-active pituitary tumours in vitro.
