Research report: Inhibin B levels in children with cryptorchidism who underwent orchidopexy after 18 months of age: a single centre cross-sectional study

Boys in Kenya who underwent surgery for undescended testes well beyond the recommended age frequently showed postoperative hormone concentrations in the lowest range of what is expected for their age, according to a cross-sectional study conducted at Kenyatta National Hospital in Nairobi. Among 69 boys who had orchidopexy after 18 months of age, 45 — or 65.2 percent — had serum inhibin B concentrations at or below the age-specific 25th percentile six months after surgery, while the remaining 24 (34.8 percent) fell above that threshold. The study, published in the African Journal of Urology, offers one of the few direct measurements of postoperative testicular hormonal markers in children operated on late in low- and middle-income settings, where delayed surgery remains common.

Cryptorchidism, the condition in which one or both testes fail to reach the scrotum, is described in the study as a common congenital abnormality of the male genital tract. Testicular descent normally occurs in two phases: a transabdominal phase between gestational weeks 8 and 15, and an inguinoscrotal phase between weeks 25 and 35. A true undescended testis lies along its normal path of descent but fails to complete the journey. International guidelines recommend that treatment begin from six months of age, because spontaneous descent becomes uncommon after that point, and that orchidopexy — the surgical fixation of the testis in the scrotum — be completed by 12 to 18 months of age. Earlier surgery has been associated with more favorable reproductive and testicular outcomes and is recommended in part to reduce long-term risks including testicular malignancy and torsion.

The reality in many African hospitals diverges sharply from that timeline. An earlier eight-month study at the Kenyatta National Hospital paediatric filter clinic found cryptorchidism in 5.4 percent of 679 patients seen. Across several African settings, researchers have repeatedly documented orchidopexy performed beyond the recommended window, with late presentation to surgical services identified as a major contributing factor. In the Democratic Republic of Congo, one team reported that 78.9 percent of patients presented at two years of age or older. At Consolata Nyeri Hospital in Kenya, the median age at presentation was reported as nine years, while a more recent Kenyatta study recorded a mean age at presentation of five years. The new study’s cohort fits this pattern: the median age at surgery was 6.75 years, with a mean of 6.0 years and a standard deviation of 3.43 — far above the globally recommended surgical window of six to eighteen months.

The researchers focused on inhibin B, a glycoprotein produced by Sertoli cells in the testes. Because its production is closely linked to the presence and maturation of germ cells, which provide paracrine signals that stimulate Sertoli cell activity, inhibin B serves as a marker of Sertoli cell function and, indirectly, of spermatogenic activity. While testicular histology obtained by biopsy remains a broadly endorsed approach for predicting future fertility, serum inhibin B has been used by several studies as a non-invasive substitute. A key complication is that inhibin B concentrations vary considerably with age throughout childhood and adolescence, so raw values cannot be interpreted in isolation. The study therefore categorized each participant against age-specific percentiles derived from a normative model published by Kelsey and colleagues, and the authors explicitly state that these percentiles were not interpreted as thresholds for testicular dysfunction or future fertility.

The study was conducted between September 1, 2024 and June 30, 2025 at the paediatric surgical unit of Kenyatta National Hospital, the largest tertiary referral hospital in Kenya, with 1,800 beds and two of its 24 theatres dedicated to paediatric surgery. Eligible participants were boys with cryptorchidism who had undergone orchidopexy after 18 months of age, were aged up to 13 years, had completed six months of postoperative follow-up, and whose parents or guardians provided informed consent. Children with disorders of sexual differentiation, syndromic or chromosomal anomalies, hormonal therapy, or anorchia discovered during surgery were excluded. Blood samples were drawn six months after surgery, between 8:00 and 11:00 in the morning, because inhibin B peaks in the early morning, and were analyzed as a batch using enzyme-linked immunosorbent assay kits from Beckman Coulter at an ISO 15189-certified laboratory. The six-month interval was chosen on the basis of comparable work showing that postoperative inhibin B rises significantly from one month after surgery and then plateaus between six and twelve months.

The percentile classification revealed a cohort skewed toward the lower end of the normative distribution. Among the 45 participants at or below the 25th percentile, the mean inhibin B concentration was 44.9 pg/mL and the median was 35.0 pg/mL, compared with higher concentrations among participants above the 25th percentile. Bilateral cryptorchidism was the most common laterality in this lower-percentile group, and 10 of the 45 participants had undergone staged orchidopexy. In the higher group, most participants had unilateral cryptorchidism and single-stage repairs, and 62.5 percent of them actually had concentrations above the 50th percentile for age. Overall, bilateral cryptorchidism was present in 24 participants (34.8 percent) and 13 (18.8 percent) underwent staged orchidopexy.

When the researchers tested whether these descriptive patterns reflected genuine associations, the answer was no. A Kruskal-Wallis test found no statistically significant difference in serum inhibin B concentrations according to testicular laterality (H = 0.22, p = 0.895), and a Mann-Whitney U test found no significant difference between staged and single-stage surgery groups (U = 327.5, p = 0.580). The authors caution that the predominance of bilateral disease in the lower-percentile group should not be over-read: the predominance is clinically relevant in light of poorer long-term reproductive outcomes reported for bilateral cryptorchidism — one study by Lee and colleagues reported infertility rates approximately 3.5 times higher among men with a history of bilateral than unilateral cryptorchidism, and more than six times higher than in controls — but the bivariate analyses in this cohort showed no significant association, and the small subgroup sizes and clinical heterogeneity demand cautious interpretation.

A scatter plot of postoperative inhibin B against age at surgery, smoothed with a locally weighted scatterplot smoothing (LOWESS) curve, illustrated the age-dependent variability of the hormone without assuming linearity. The curve showed non-linear variation across the age range: a decline from early to mid-childhood, a rise around ten years of age, and a subsequent tapering. The authors argue that this pattern reinforces the need to interpret postoperative concentrations relative to age-specific normative values rather than raw numbers. They also place their findings alongside earlier work: Raman and colleagues reported postoperative increases in inhibin B levels and percentile scores among children over two years of age at surgery, and Irkilata and colleagues reported significant increases in both early and late orchidopexy groups, with changes related to testicular histology. Neither of those analyses accounted for age-specific normative values, however, limiting direct comparison with the age-adjusted percentile approach used here.

The study’s limitations are substantial and the authors enumerate them carefully. The sample was small, particularly within subgroups, which may have limited statistical power and generalizability. Inhibin B was measured at a single postoperative time point, precluding any assessment of change over time, and there were no preoperative measurements and no comparison group of boys operated on within the guideline-recommended age range — so the study cannot determine whether the observed postoperative distribution was related to surgical timing. The cohort was clinically heterogeneous: congenital and acquired (ascending) cryptorchidism were not systematically distinguished, retractile testes were not separately documented, and age at orchidopexy therefore cannot be assumed to represent the duration of cryptorchidism. In boys with unilateral disease, the normally descended contralateral testis may contribute substantially to circulating inhibin B. Tanner stage, testicular volume, testicular position and palpability were not systematically assessed, testicular histology was unavailable, and long-term reproductive outcomes such as semen parameters and paternity were beyond the study’s scope.

The authors conclude that a substantial proportion of boys undergoing orchidopexy after 18 months of age had postoperative inhibin B concentrations at or below the age-specific 25th percentile, but stress that these measurements should be interpreted descriptively rather than as evidence of impaired or preserved testicular function, and not as direct predictors of future fertility. They recommend that current guidance for surgery within the recommended age continue to be promoted, with strategies to improve early recognition, timely referral and access to surgical care in settings where late orchidopexy is frequent. Future prospective studies, they write, should include preoperative and serial postoperative inhibin B measurements, appropriately characterized comparison groups operated on within the recommended window, separation of congenital from acquired cases, analysis of unilateral and bilateral disease separately where sample size permits, and incorporation of Tanner stage, testicular volume, position and hormonal measurements, with longitudinal follow-up into adulthood to clarify the relationship between surgical timing, inhibin B and definitive reproductive outcomes.

Subject of Research: Postoperative serum inhibin B concentrations in boys undergoing late orchidopexy for cryptorchidism at a Kenyan tertiary hospital

Article Title: Inhibin B levels in children with cryptorchidism who underwent orchidopexy after 18 months of age: a single centre cross-sectional study

Article References: Bichanga, B., Jumbi, T., Osawa, F., & Mwika, P. (2026). Inhibin B levels in children with cryptorchidism who underwent orchidopexy after 18 months of age: a single centre cross-sectional study. African Journal of Urology, 32(1), Article 70. https://doi.org/10.1186/s12301-026-00617-y

Image Credits: AI Generated

DOI: 10.1186/s12301-026-00617-y

Keywords: cryptorchidism, orchidopexy, inhibin B, Sertoli cells, Kenyatta National Hospital, testicular function, delayed surgery, pediatric urology, low- and middle-income countries, age-specific percentiles, fertility markers, cross-sectional study