The source of plasma dihydrotestosterone in man

Area of Science:

• Endocrinology
• Androgen Metabolism
• Steroid Biochemistry

Background:

• Plasma dihydrotestosterone (DHT) is a potent androgen.
• Understanding the peripheral precursors of DHT is crucial for comprehending androgen action.

Purpose of the Study:

• To investigate the relative contributions of testosterone (T) and androstenedione (A) as precursors to plasma DHT in humans.
• To determine the metabolic clearance rates (MCR) and production rates of DHT.

Main Methods:

• Infusion of labeled testosterone and androstenedione into human subjects.
• Measurement of plasma hormone levels using competitive binding assays.
• Calculation of metabolic clearance rates, conversion ratios, and transfer constants.

Main Results:

• Testosterone is the primary precursor for plasma DHT in males, accounting for at least 70% of production.
• Androstenedione is a major precursor for plasma DHT in females, contributing at least two-thirds of the circulating levels.
• Metabolic clearance rate of DHT is significantly lower than that of testosterone.

Conclusions:

• Plasma DHT primarily originates from peripheral conversion of testosterone and androstenedione.
• Testosterone is the dominant precursor in males, while androstenedione is more significant in females.
• DHT levels in circulation may reflect androgen metabolism within peripheral target tissues rather than direct glandular secretion.