Follicle‐stimulating hormone plays a crucial role in spermatogenesis. The aim of this study was to evaluate the efficacy of treatment with FSH in Chinese infertility population.

Prospective, randomized, double‐blind, placebo‐controlled clinical study.

A total of 354 men affected by idiopathic oligozoospermia from three medical centres.

This study contained three parts: (i) treatment with different doses of rhFSH (50 IU, 100 IU, 200 IU and 300 IU); (ii) the efficacy of rhFSH at different periods (2, 3, 4, 5 months); (iii) FSH treatment in patients with different levels of inhibin B (normal‐level group, low‐level group and high‐level group). Semen parameters were evaluated in all subjects. The patients who had not reached spontaneous pregnancy underwent assisted reproductive techniques.

Sperm number was significantly increased after treatment with FSH at doses of at least 200 IU, and the improvement was observed beginning at the third month. The significant improvement in both morphology and forward motility was observed beginning at the fifth month. Moreover, 300 IU rhFSH administration for 5 months could significantly improve the spontaneous pregnancy rate (12/40) and ART pregnancy rate (14/28), while the rates for placebo group were two of twenty‐nine and five of twenty‐seven, respectively. The seminal parameters (total sperm count, sperm concentration, forward motility and morphology) were significantly improved in the normal‐ and low‐level inhibin B groups, but no significant variation was observed in the high‐level group at the end of the study.

The efficacy of FSH treatment was associated with the dose of FSH and duration of treatment, and FSH therapy was more effective in patients with normal level and low level of inhibin B.