Demystifying the Relevance of Size Amongst Macro- and Micro-Corticotropinoma: Experience in 206 Patients

In individuals with adrenocorticotrophic hormone (ACTH)-dependent Cushing's syndrome (CS), to estimate the differences between micro-corticotropinoma (size ≤6 mm and 6-10 mm), macro-corticotropinoma (>10 mm) and ectopic Cushing's syndrome (ECS), in relation to their epidemiological, clinical and biochemical parameters.

In individuals with CS, the clinical and hormonal parameters, and magnetic resonance imaging of sella were collected from 1984 to 2019. A total of 138 cases of micro-corticotropinoma, 47 cases of macro-corticotropinoma and 21 cases of ECS were compared.

Except for size, there were no differences in biochemical and hormonal parameters of macro- and micro-corticotropinoma, irrespective of their size (≤6 mm, 6-10 mm and >10 mm). In comparison to Cushing's disease (CD), individuals with ECS had a male predominance (F:M ratio of 2.4:1 vs. 0.5:1), shorter duration from onset of symptoms to diagnosis (24 vs. 12 months). They also had a higher ACTH (139 vs. 65.8 pg/ml), 0800h cortisol (1200 vs. 880 nmol/l), 2300h cortisol (1100 vs. 700 nmol/l) and cortisol levels after high dose dexamethasone suppression test (1050 vs. 244.5 nmol/l).

The biochemical phenotype of macro-corticotropinoma resembles that of micro-corticotropinoma despite their larger tumour size, suggesting that the former is relatively less functional. Micro-corticotropinoma ≤6 mm and 6-10 mm have a similar clinical and biochemical profile. As compare to CD, ECS is characterised by a higher disease burden as reflected in their higher cortisol, more autonomicity and loss of rhythmicity.