Endocrine analysis of childhood monorchism

We characterized follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels in boys with surgically documented unilateral absent testes (monorchism) to determine whether measurement of gonadotropin levels could distinguish them from boys with unilateral impalpable cryptorchidism.

Baseline serum gonadotropin levels were prospectively measured in 43 boys 2 months to 14 years old who presented with a unilateral impalpable testis that was confirmed to be absent at surgery. Control serum specimens were obtained from 63 age matched boys undergoing minor surgery with no evidence of hypospadias, or testicular, hormonal or renal diseases. Serum FSH and LH levels were drawn preoperatively and assayed by double antibody radioimmunoassay. A subgroup of 7 boys with monorchism was also evaluated following gonadotropin-releasing hormone (GnRH) stimulation and compared to age matched boys with a unilaterally impalpable testis discovered surgically.

In the monorchism group mean plus or minus standard deviation basal FSH was 4.08 +/- 0.28 mIU/ml. and LH was 4.13 +/- 0.33 mIU/ml. In the control group mean basal FSH was 4.36 +/- 1.52 mIU/ml. and LH was 4.66 +/- 0.75 mIU/ml. No statistical difference existed between the 2 groups for mean basal gonadotropin level. While monorchid boys were more likely to have elevated FSH levels (p = 0.016), this was not true for LH (p = 0.21). Since gonadotropin levels less than 5 mIU/ml. are accepted normal values, this threshold was applied to FSH and carried a sensitivity of 23.8%, specificity 93.8%, positive predictive value 71.4% and negative predictive value 65.6%. Lower cutoff values marginally improved sensitivity but reduced specificity. Peak stimulated levels of FSH and LH following GnRH stimulation failed to distinguish between boys with 1 or 2 testes.

Baseline FSH is more likely to be elevated in prepubertal boys with monorchism but it does not appear to be clinically useful when sensitivity and predictive value are poor. Similarly, gonadotropin level following GnRH stimulation is not sufficiently sensitive to advocate the use of hormonal measurements to diagnose prepubertal monorchism.