ENDOCRINE ANALYSIS OF CHILDHOOD MONORCHISM

Purpose: We characterized follicle-stimulating hormone (FSH) and lutei nizing hormone (LH) levels in boys with surgically documented unilater al absent testes (monorchism) to determine whether measurement of gona dotropin levels could distinguish them from boys with unilateral impal pable cryptorchidism. Materials and Methods: Baseline serum gonadotrop in levels were prospectively measured in 43 boys 2 months to 14 years old who presented with a unilateral impalpable testis that was confirm ed to be absent at surgery. Control serum specimens were obtained from 63 age matched boys undergoing minor surgery with no evidence of hypo spadias, or testicular, hormonal or renal diseases. Serum FSH and LH l evels were drawn preoperatively and assayed by double antibody radioim munoassay. A subgroup of 7 boys with monorchism was also evaluated fol lowing gonadotropin-releasing hormone (GnRH) stimulation and compared to age matched boys with a unilaterally impalpable testis discovered s urgically. Results: In the monorchism group mean plus or minus standar d 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/m l. and LH was 4.66 +/- 0.75 mIU/ml. No statistical difference existed between the 2 groups for mean basal gonadotropin level. While monorchi d 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 predic tive value 71.4% and negative predictive value 65.6%. Lower cutoff val ues marginally improved sensitivity but reduced specificity. Peak stim ulated levels of FSH and LH following GnRH stimulation failed to disti nguish between boys with 1 or 2 testes. Conclusions: Baseline FSH is m ore likely to be elevated in prepubertal boys with monorchism but it d oes not appear to be clinically useful when sensitivity and predictive value are poor. Similarly, gonadotropin level following GnRH stimulat ion is not sufficiently sensitive to advocate the use of hormonal meas urements to diagnose prepubertal monorchism.