PURPOSE: An impaired germ cell number per tubular cross-section (G/T) at orchidopexy indicates a high risk of infertility. A recent study in boys with bilateral cryptorchidism showed a very high predictive value for a low serum inhibin-B level, indicating bilateral impaired G/T. Several other studies have shown a fairly strong correlation between inhibin-B and G/T. We aimed to evaluate if inhibin-B levels at orchidopexy improved at follow-up in boys with unilateral cryptorchidism.

METHODS: We included 280 boys with unilateral non-syndromic cryptorchidism at the median age of 1 year (4 months-9 years) who underwent orchidopexy. They were evaluated for serum FSH, LH and inhibin-B levels at surgery and at follow-up (median 16 months later), including multiple of the median (MoM) estimations of inhibin-B due to the age dependency of normal levels.

RESULTS: The inhibin-B MoM score improved significantly at follow-up. At orchidopexy, 59 (21%) boys had inhibin-B levels below the normal 2.5-percentile indicating impaired G/T bilaterally. At follow-up, 36% of the boys still had low inhibin-B. At orchidopexy, 221 (79%) boys had inhibin-B levels above normal 2.5-percentile and only 5% had low inhibin-B levels at follow-up. The risk of low inhibin-B levels at follow-up was significantly different between the two groups (p < 0.0001). At follow-up, totally, 32 (11%) boys had low inhibin-B levels, hereof only 3 patients with increased FSH.

CONCLUSIONS: Orchidopexy benefits the fertility potential. About 10% of boys with unilateral non-syndromic cryptorchidism may have a bilateral testicular disease reducing their fertility potential. Insufficient gonadotropin stimulation may possibly be the cause.