Changes in glucose metabolism based on 75-g oral glucose tolerance tests before and after surgery for adrenal Cushing's syndrome

Genotype-negative multiple endocrine neoplasia type 1 with prolactinoma, hyperparathyroidism, and subclinical Cushing's syndrome accompanied by hyperglycemia: a case report

Background

Multiple endocrine neoplasia type 1 (MEN1) is a rare autosomal dominant disorder, accompanied by multiple endocrine neoplasms of the parathyroid, pancreas, pituitary, and other neoplasms in the adrenal glands. However, in some cases, patients clinically diagnosed with MEN1 may be genotype-negative.

Case presentation

A 56-year-old female was diagnosed with MEN1 based on a macroprolactinoma (19 mm in diameter), primary hyperparathyroidism, and a cortisol-producing adrenal adenoma, without a family history. At first appearance, she had a hemoglobin A1c of 12.0% and a fasting plasma glucose level of 16.3 mmol/L (294 mg/dL). She complained of headaches and had a history of prolactinoma at 28 years of age, with concomitant elevated prolactin 1102.0 μg/L (ng/mL). Insulin therapy was initiated for glucose management following the administration of an oral hypoglycemic agent. Additionally, cabergoline was initiated for due to the prolactinoma, resulting in a normalized prolactin level. Thereafter, medication for diabetes could be withdrawn. Subsequently, surgery was performed for primary hyperparathyroidism and the cortisol-producing adrenal adenoma, which was consistent with the preoperative diagnosis. Additionally, a thyroid tumor resected with primary hyperparathyroidism revealed to be invasive papillary thyroid carcinoma (PTC). Target gene testing revealed a negative genotype for MEN1 gene, with only one common polymorphism that was non-pathogenic.

Conclusions

Genotype-negative MEN1 typically has a favorable clinical course without a third primary MEN1 manifestation. However, the present case had a symptomatic macroprolactinoma with an apparent elevated glucose level and three manifestations of tumors (pituitary, parathyroid, and adrenal) with invasive PTC, and a delayed diagnosis could have caused crucial deterioration. Clinicians should pay attention to the clinical features of MEN1 including glucose intolerance. In such cases, the treatment of endocrine disorders can lead to the normalization of the glucose level.

Cortisol secretion and abnormalities of glucose metabolism in nondiabetic patients with hypertension

OBJECTIVE

Glycometabolic changes are associated with hypercortisolism in Cushing's syndrome. Because impaired glucose tolerance (IGT) and insulin resistance are frequently detected in patients with essential hypertension, we hypothesized that in these patients, early glycometabolic abnormalities might be related to differences in regulation of cortisol secretion.

METHODS

In a cross-sectional study, we included 155 nondiabetic, essential hypertensive patients who were free of organ complications. The homeostasis model assessment (HOMA) index and the area under the curve of plasma glucose (AUC-glucose) and insulin (AUC-insulin) concentration following an oral glucose tolerance test were measured, together with daily plasma cortisol (8 a.m., 3 p.m. and 12 a.m.; AUC-cortisol) and 8 a.m. cortisol after 1 mg overnight dexamethasone suppression test (DST).

RESULTS

IGT was present in 27% of patients who were older and had higher BMI, plasma triglycerides and uric acid, AUC-cortisol and DST-cortisol, and lower HDL-cholesterol. Frequency of IGT increased progressively across tertiles of DST-cortisol, together with levels of glycated hemoglobin, fasting insulin and C-peptide, HOMA-index, AUC-glucose, and AUC-insulin. AUC-cortisol and DST-cortisol were directly correlated with insulin, C-peptide, HOMA-index, AUC-glucose, and AUC-insulin. Multivariate regression analysis showed that DST-cortisol was directly and independently correlated with HOMA index, AUC-glucose, and AUC-insulin. In a logistic regression model, both AUC-cortisol and DST-cortisol independently predicted IGT.

CONCLUSION

Daily cortisol and cortisol response to DST are independent determinants of IGT and insulin resistance in nondiabetic patients with hypertension, suggesting that even subtle differences in regulation of cortisol secretion might increase the risk of these patients to develop diabetes.

Characteristics of aldosterone-producing adenomas in patients without plasma renin activity suppression

Primary aldosteronism (PA) usually accompanies suppressed plasma renin activity (PRA) through a negative feedback mechanism. While some cases of PA with unsuppressed PRA were reported, there have been no studies about the characteristics of PA with unsuppressed PRA; thus, these characteristics were examined herein. Nine patients with unsuppressed PRA and 86 patients with suppressed PRA were examined. All patients underwent segmental adrenal venous sampling (sAVS) and adrenalectomy, and were pathologically confirmed to have cytochrome P450 11B2 (CYP11B2)-positive aldosterone-producing adenoma according to international histopathology consensus criteria. Unsuppressed and suppressed PRA were defined as PRA levels of > 1.0 and ≤ 1.0 ng/mL/hr, respectively, in multiple blood samples obtained in the resting position. The unsuppressed PRA group had higher morning cortisol levels (12.6 [8.5, 13.5] vs. 8.5 [7.1, 11.0] μg/dL, P = 0.03) and higher cortisol levels after a 1 mg dexamethasone suppression test (DST) (2.2 [1.6, 2.5] vs. 1.3 [1.0, 1.9] μ g/dL, P = 0.004) than the suppressed PRA group. The unsuppressed PRA group also showed higher aldosterone levels on the non-surgical side during sAVS (P = 0.02 before adrenocorticotropic hormone (ACTH) stimulation, P = 0.002 after ACTH stimulation), a higher intensity of CYP17 expression in the resected adrenal gland (P = 0.02), and a lower clinical complete success rate 1 year after surgery (P = 0.04) compared with those in the suppressed PRA group. These findings suggest that PA should not be ruled out by unsuppressed PRA among patients with hypertension, particularly when their cortisol levels remain unsuppressed in the 1 mg DST. Meanwhile, it should be acknowledged that patients with unsuppressed PRA have higher aldosterone levels on the non-surgical side, and a lower likelihood of postoperative complete clinical success is to be expected.