Serum LH correlates highly with intratesticular steroid levels in normal men

Abstract

Sex steroids are essential for spermatogenesis; however, normal intratesticular concentrations of these hormones in man have not been extensively studied. To improve our understanding of intratesticular hormone concentrations, we performed bilateral testicular aspirations in a group of normal men, determined sex steroid concentrations within each testis, and compared these levels to serum hormone concentrations. Ten healthy human subjects aged 20-49 underwent bilateral testicular aspirations. Intratesticular hormone concentrations of testosterone, dihydrotestosterone (DHT), and estradiol were measured using liquid chromatography-tandem mass spectrometry. Intratesticular testosterone concentrations ranged from 119 to 1251 ng/mL, with a mean of 635 +/- 368 ng/mL. Intratesticular estradiol ranged from 0.41 to 3.9 ng/mL, with a mean of 2.4 +/- 1.3 ng/mL. Intratesticular DHT ranged from 1.1 to 7.9 ng/mL, with a mean of 3.5 +/- 3.2 ng/mL. Intratesticular testosterone and estradiol concentrations correlated highly with serum luteinizing hormone (LH; r = 0.87 and r = 0.70 respectively, P < .01). Intratesticular testosterone correlated highly with serum testosterone. Moreover, a significant correlation between the right and left testes was observed for testosterone (r = 0.82, P = .003), but not for estradiol or DHT. Intratesticular hormone concentrations can be safely assessed by testicular aspiration. Intratesticular testosterone and estradiol correlate highly with serum LH concentrations, and variation in serum LH accounts for most of the variation in intratesticular testosterone among men. In addition, intratesticular testosterone is highly correlated between testes in a given individual. Direct measurement of intratesticular testosterone will improve our understanding of the relationship between intratesticular sex steroids and spermatogenesis, and may have implications for the development of male hormonal contraception.

Figure 1

The relationships between serum luteinizing hormone (LH) and intratesticular testosterone (A), LH and intratesticular estradiol (B), follicle-stimulating hormone (FSH) and intratesticular testosterone (C), and FSH and intratesticular estradiol (D) in 10 normal men undergoing testicular aspiration.

Figure 2

The relationships between intratesticular testosterone and serum testosterone (A), intratesticular dihydrotestosterone (DHT) and serum DHT (B), and intratesticular estradiol and serum estradiol (C) in 10 normal men undergoing testicular aspiration.

Figure 3

The relationships between right and left testes of intratesticular testosterone (A), intratesticular dihydrotestosterone (B), and intratesticular estradiol (C) in 10 normal men undergoing testicular aspiration.