Metabolic clearance rate and blood production rate of testosterone and dihydrotestosterone in normal subjects, during pregnancy, and in hyperthyroidism.
Level 4 - case-series / case-control
Small cross-sectional comparative physiological study
PubMed 5020435 · doi:10.1172/JCI106917
What was done
Metabolic clearance rate (MCR), blood production rate, conversion of plasma testosterone (T) to dihydrotestosterone (DHT), and renal clearance of androstenedione, T, and DHT were measured in 8 normal men, 7 normal females, 5 pregnant females, 5 females with hyperthyroidism, and 3 patients with testicular feminization syndrome.
What was found
In normal men, MCR(T) was 516 +/- 108 L/m2/day and MCR(DHT) was 391 +/- 71 L/m2/day; T-to-DHT conversion was 2.8 +/- 0.3% and DHT production was 0.39 +/- 0.1 mg/day (50% from plasma T). In normal females, MCR(T) was 304 +/- 53 L/m2/day, MCR(DHT) was 209 +/- 45 L/m2/day, T-to-DHT conversion was 1.56 +/- 0.5% (all lower than men, P < 0.001), and DHT production was 0.05 +/- 0.028 mg/day (10% from plasma T). In pregnant females, MCR(T) (192 +/- 36 L/m2/day), MCR(DHT) (89 +/- 30 L/m2/day), and conversion (0.72 +/- 0.15%) were significantly lower than in nonpregnant females, with production rates unchanged. In hyperthyroid females, MCRs were similar to pregnant females, but conversion was higher (2.78 +/- 1.7%). In testicular feminization, MCRs were greatly reduced compared to normal females, while conversion was in the male range. Urinary DHT and androstenedione derived <20% and <10% from plasma, respectively.
Why it matters
This study defines baseline kinetic parameters of testosterone and dihydrotestosterone clearance and interconversion in humans, showing how altered endocrine states like pregnancy and hyperthyroidism affect androgen metabolism.
Limits
Sample sizes per subgroup are very small (3 to 8 subjects). The testicular feminization subgroup is heterogeneous (one adult with hyperthyroidism and two children). The abstract does not provide complete inferential statistical testing for all reported subgroup comparisons.
Cited by
- supports Women typically produce about one-tenth the amount of androgens that men produce.