Plasma cortisol profiles in Cushing's syndrome

Area of Science:

• Endocrinology
• Internal Medicine
• Biochemistry

Background:

• Cushing's syndrome presents diagnostic challenges due to varied etiologies.
• Differentiating between Cushing's disease and adrenal adenoma is crucial for effective treatment.
• Understanding hormonal secretion patterns can improve diagnostic accuracy.

Purpose of the Study:

• To investigate and compare plasma cortisol and ACTH secretory patterns in patients with Cushing's disease (CD) and adrenal adenoma (AA).
• To determine if frequent sampling of plasma cortisol and ACTH can aid in differentiating the causes of Cushing's syndrome.
• To assess the utility of short-term (6-hour) hormonal profiling.

Main Methods:

• Frequent blood sampling to measure plasma cortisol levels in patients with CD, AA, and a case of bronchogenic carcinoma.
• Radioimmunoassay (RIA) measurement of plasma ACTH at 10-minute intervals in select subjects.
• Calculation of coefficients of variation for plasma cortisol concentrations to assess secretory patterns.

Main Results:

• Cushing's disease (CD) exhibited distinct episodic secretion of cortisol and ACTH, with cortisol variation coefficients of 24-27% and mean ACTH of 94 pg/ml.
• Adrenocortical adenoma (AA) showed cortisol secretion at a constant rate with minimal fluctuation (cortisol variation 8-14%) and near-zero ACTH levels.
• A patient with bronchogenic carcinoma had a cortisol variation coefficient of 14%, similar to AA, highlighting the need for comprehensive pattern analysis.

Conclusions:

• Distinct episodic secretory patterns of cortisol and ACTH are characteristic of Cushing's disease.
• Constant cortisol secretion with minimal ACTH levels is indicative of adrenocortical adenoma.
• Plasma cortisol and ACTH secretory profiles, even over short periods, are valuable tools for differentiating the etiologies of Cushing's syndrome.