Testosterone and 5alpha-androstan-17beta-ol-3-one (DHT) levels in man

Area of Science:

• Endocrinology
• Androgen Metabolism
• Hormone Physiology

Background:

• Plasma dihydrotestosterone (DHT) levels are often considered alongside testosterone (T) levels to assess androgenicity.
• The relationship between T and DHT, particularly the T/DHT ratio, requires further investigation across different physiological and pathological conditions.

Purpose of the Study:

• To test the hypothesis that plasma DHT levels are an androgenicity parameter independent of T levels.
• To determine if the T/DHT ratio is influenced by sex, T levels, or the origin of T (endogenous vs. exogenous).
• To investigate the role of the liver in DHT production and metabolism.

Main Methods:

• Determined the T/DHT ratio in males and females under conditions of low and high plasma T levels.
• Administered exogenous testosterone via intramuscular injection (short/long-acting esters) and oral administration.
• Studied patients with liver conditions (porto-caval shunt, cirrhosis) and a patient with testicular feminization syndrome.

Main Results:

• The T/DHT ratio was found to be a function of T levels, not sex, irrespective of T's origin.
• In patients with bypassed liver circulation, oral T administration led to higher DHT levels than expected, suggesting extra-hepatic DHT origin or reduced hepatic DHT metabolism.
• A patient with testicular feminization syndrome exhibited normal T/DHT ratios under basal and stimulated conditions.

Conclusions:

• Plasma DHT levels are not an androgenicity parameter entirely independent of T levels, as the T/DHT ratio is T-level dependent.
• Liver function plays a crucial role in regulating plasma DHT levels, with evidence supporting extra-hepatic DHT production or decreased hepatic metabolism.
• The T/DHT ratio appears consistent in individuals with specific endocrine conditions like testicular feminization syndrome.