Dynamic changes in LH/FSH ratios in infants with normal sex development.

Objective: Little is known about the ratio between luteinizing hormone (L H) and follicle-stimulating hormone (FSH) during infancy. This study aimed to evaluate serum and urinary LH/FSH as a marker of sex with age-specific cutoffs in healthy infants. Design: A prospective, longitudinal cohort study of healthy infants ag ed 0-1.2 years. Methods: In total, 236 healthy infants (122 boys and 114 girls) from The COPENHAGEN Minipuberty Study (ClinicalTrials. gov ID: NCT02784184), with 567 serum and 603 urine samples, wer e included. Measures of diagnostic accuracy, including sensitivity and specificity, were used to assess the a bility of LH/FSH to detect sex in healthy infants. Results: In both serum and urine, LH/FSH was highest in males with mini mal overlap between the sexes. In contrast to isolated LH and FSH concentrations, LH/FSH ratios in both serum and urine were excellent markers of sex from 0 to 1.2 years with median sensitivities and specificities ranging fr om 93 to 100% with correspondingly narrow 95% CIs. Conclusions: Serum and urinary LH/FSH ratios are excellent discriminators of sex in healthy infants during the entire first year of life. The clinical role and application of the rat io remain to be elucidated. [ABSTRACT FROM AUTHOR]