Cushing’s disease: a comparison of pituitary corticotroph microadenomas and macroadenomas

Cushing’s disease appears as a functionally heterogeneous disease, but criteria that are able to distinguish between different clinical forms remain elusive. We compared two subgroups of patients with proven Cushing’s disease according to the size of the pituitary adenoma, evaluated by computed tomography or magnetic resonance imaging. Our series comprised 11 patients with a microadenoma and 10 with a macroadenoma (median volumes (range): 173 (13–270) and 3022 (500–10312) mm3 respectively; P < 0:0001). The clinical presentation was similar in the two groups, but the time elapsed before diagnosis was longer, and visual impairment was less frequent in the patients with a microadenoma (1:5 6 0:8 years and 0%) than in those with a macroadenoma (0:7 6 0:6 years and 40%; P < 0:05). Morning and evening peripheral concentrations of ACTH were greater in patients with macroadenoma (134 6 78 and 130 6 7 ng/l respectively) than in those with microadenoma (52 6 28 and 56 6 19 ng/l, P < 0:05). Hypokalaemia and lymphopenia were also more pronounced in patients with macroadenoma (3:4 6 0:3 mmol/l and 1273 6 401 lymphocytes/mm3) than in those with microadenoma (3:8 6 0:3 mmol/l and 18526668 lymphocytes/mm3; P < 0:05), although morning and evening plasma cortisol concentrations were similar in both groups. In patients wit