Endocrine Abstracts

Background: The majority of adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas are less than 10 mm in diameter and are described as microadenomas, while corticotroph macroadenomas (≥10 mm) are a less common cause of Cushing’s disease. Prior reports on the differences of clinical and biochemical behavior of corticotroph microadenomas and macroadenomas were inconsistent.

Objective: Describe the clinical and biochemical characteristics of patients with corticotroph macroadenomas and microadenomas.

Methods: Retrospective charts review of patients with Cushing’s disease treated at Rabin Medical Center between 2000 and 2017, or at Maccabi Healthcare Services in Israel between 2005 and 2017. Tumors in which the largest diameter was ≥10 mm were considered to be macroadenomas. When no visible tumor was seen on MRI, the tumor was considered to be a microadenoma. Epidemiologic, clinical and biochemical factors were compared between patients with corticotroph macroadenomas and microadenomas.

Results: The cohort included 105 patients (82 women, 78%; mean age ± SD, 41.5 ± 14.5 years), including 68 patients (64.8%) with a pituitary microadenoma (mean size, 5.2±2.2 mm), 25 patients (23.8%) with a macroadenoma (mean size, 18.0±7.7 mm), and 12 patients with no visible adenoma. Baseline characteristics were similar between the groups, including age, gender, body mass index, and comorbidities. Most common reasons for completing an investigation for Cushing’s syndrome among patients with microadenomas and macroadenomas were weight gain (46.3% vs 52.0%, P=NS) and Cushingoid features (27.5% vs 20.0%, P=NS). While mean urinary free cortisol levels (5.2 ± 5.4 ULN vs 7.8 ± 8.7 ULN) and mean serum cortisol levels following low-dose dexamethasone suppression test (487.6 ± 329.8 vs 372.0 ± 324.5 nmol/l, respectively), were higher among patients with macroadenomas, the differences were not statistically significant and there was considerable overlap between the two groups. Concentrations of ACTH were greater in patients with macroadenoma than in those with microadenoma (1.9 ± 1.2 ULN vs 1.3 ± 0.8 ULN, respectively, P =0.01). Most patients in both groups underwent transsphenoidal surgery, and rates of recurrent or persistent disease were similar in patients with microadenomas and macroadenomas (35.2% vs 28.6%, respectively; P=NS). The rate (83.9% vs 83.3%, respectively) and duration (9.4 ± 8.3 vs 9.7 ± 11.9 months, respectively) of post-operative glucocorticoid treatment were similar in both groups.

Conclusions: While ACTH-secreting macroadenomas exhibit higher plasma ACTH levels than microadenomas, there was no correlation between tumor size with cortisol secretion values or clinical characteristics in patients with Cushing’s disease.