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Plasma immunoassayable ACTH levels during and after hydrocortisone infusion in patients with Cushing's disease
Insights
Patients with Cushing's disease show delayed plasma ACTH suppression after hydrocortisone infusion compared to those with primary adrenocortical insufficiency, indicating altered adrenal-pituitary feedback.
Area of Science:
- Endocrinology
- Hormone Regulation
- Adrenal Gland Physiology
Background:
- Cushing's disease involves excess cortisol production, leading to altered feedback mechanisms.
- Primary adrenocortical insufficiency results from inadequate cortisol production.
- Adrenocorticotropic hormone (ACTH) plays a crucial role in regulating cortisol synthesis.
Purpose of the Study:
- To compare the plasma ACTH response to exogenous hydrocortisone infusion in patients with Cushing's disease versus primary adrenocortical insufficiency.
- To investigate the differences in negative feedback sensitivity of the pituitary-adrenal axis.
Main Methods:
- Intravenous hydrocortisone infusion at two different doses (1.0 mg/kg/1.5 hr and 0.5 mg/kg/1.5 hr).
- Measurement of plasma ACTH levels at various time points before and after hydrocortisone administration.
- Comparison of ACTH suppression dynamics between patient groups.
Main Results:
- Patients with primary adrenocortical insufficiency exhibited exponential ACTH suppression following hydrocortisone.
- In contrast, patients with Cushing's disease demonstrated delayed ACTH suppression.
- ACTH levels were significantly less suppressed in Cushing's disease patients at 90 and 120 minutes post-infusion (p<0.05).
Conclusions:
- The pituitary-adrenal axis in Cushing's disease exhibits impaired negative feedback sensitivity to hydrocortisone.
- These findings highlight distinct differences in hormonal regulation between Cushing's disease and primary adrenocortical insufficiency.
Abstract:
The plasma ACTH responses to hydrocortisone infusion were compared in patients with Cushing's disease and primary adrenocortical insufficiency. In 4 patients with primary adrenocortical insufficiency, plasma ACTH levels were suppressed exponentially after administration of a relatively large dose of hydrocortisone (1.0 mg/kg/1.5 hr-3.0 mg/kg/2 hr). In patients with post-adrenalectomized Cushing's disease (4, bilateral; 1, unilateral), plasma ACTH suppression was delayed. Plasma ACTH levels, expressed as a percentage of the basal concentrations, were significantly less suppressed in patients with Cushing's disease than in patients with primary adrenocortical insufficiency 90 (p less than 0.05) and 120 (p less than 0.05) min after the beginning of infusion. When 0.5 mg/kg hydrocortisone was infused over a period of 1.5 hr, suppression was also delayed in Cushing's disease, and plasma ACTH levels were less suppressed in 4 patients with Cushing's disease than in 4 patients with primary adrenocortical insufficiency at 30 (p greater than 0.05), 45 (p greater than 0.05) 60 (p less than 0.05) min.