In previous studies of testicular biopsy tissue from healthy men, intratesticular testosterone (ITT) has been shown to be much higher than serum testosterone (T), suggesting that high ITT is needed relative to serum T for normal spermatogenesis in men. However, the quantitative relationship between ...

Older men, particularly those with low serum testosterone (T) levels, might benefit from T therapy to improve bone mineral density (BMD) and reduce fracture risk. Concerns exist, however, about the impact of T therapy on the prostate in older men. We hypothesized that the combination of T and ...

Monthly injections of testosterone undecanoate (TU) act as a male contraceptive by reversibly suppressing spermatogenesis to azoospermia or severe oligoazoospermia in 95% of Chinese men. In 5% of Chinese men, however, monthly TU administered alone fails to suppress spermatogenesis into contraceptive ...

Testosterone (T) therapy in older men with low serum T levels increases lean body mass and decreases fat mass. These changes might improve physical performance and strength; however, it has not been established whether T therapy improves functional outcome in older men. Moreover, concerns exist ...

Weekly intramuscular administration of testosterone esters such as testosterone enanthate (TE) suppresses gonadotropins and spermatogenesis and has been studied as a male contraceptive. For unknown reasons, however, some men fail to achieve azoospermia with such regimens. We hypothesized that either ...

Acyline is a novel GnRH antagonist found in animal studies to be a potent suppressor of circulating gonadotropin and testosterone (T) levels. We conducted the first study of acyline administration to humans. Eight healthy, eugonadal young men were administered a series of acyline injections (0, ...

We postulated that the addition of a combined types I and II, 5alpha-reductase inhibitor (dutasteride) or long-acting GnRH antagonist (acyline) to combination testosterone plus levonorgestrel treatment may be advantageous in the suppression of spermatogenesis for male contraception. This study aimed to examine effects of novel ...

We examined the effects of sex steroids on cognitive functioning by exogenously manipulating circulating T levels in a group of healthy young men. Thirty-two men were randomized to receive 8 wk of treatment including: 1) im T enanthate 100 mg/wk plus daily oral placebo (T); 2) im placebo/wk plus ...

The development of a safe, well-tolerated, effective, and reversible male hormonal contraceptive would be a major clinical advance for couples planning their family size and for control of population growth. High-dosage parenteral testosterone (T) esters alone or in combination with a progestogen ...

Acyline is a novel GnRH antagonist that reliably inhibits gonadotropins and testosterone (T) levels in men for 48 h after a single dose up to 75 microg/kg. In this study we examined gonadotropin and T levels in 28 healthy young men administered acyline as single doses of 150 or 300 microg/kg or serial injections of 75 microg/kg. ...