Changes in serum inhibin, activin and follistatin concentrations during puberty in girls

Serum concentrations of inhibin A, inhibin B, activin A and follistatin wer e determined using two-site enzyme-linked immunosorbent assays (ELISA) duri ng pubertal ovarian development in 28 girls and five follicular phase women . Blood obtained every 15 to 20 min overnight was pooled for peptide determ ination. Serum inhibin A concentrations increased in mid puberty, exhibitin g positive correlations with bone age (r = 0.527, P = 0.0016) and oestradio l concentrations (r = 0.581, P = 0.0005). Inhibin B concentrations peaked i n mid puberty and declined thereafter, but remained greater than concentrat ions seen in prepubertal girls, and correlating positively with oestradiol (r = 0.362, P = 0.046) and follicle stimulating hormone (FSH) concentration s (r = 0.369, P = 0.038). Total activin A concentrations did not vary signi ficantly across pubertal stages. Total follistatin concentrations, determin ed by radioimmunoassay, decreased with advancing puberty, exhibiting negati ve correlations with bone age (r = -0.634, P = 0.0001) and oestradiol conce ntration (r = -0.687, P = 0.0001). Follistatin concentrations determined by an ELISA specific for follistatin 288 were greatest in mid-pubertal girls, but concentrations in late puberty were less than those in early puberty. The free follistatin assay indicated that all circulating follistatin was a ctivin-bound. These results suggest that significant changes in serum conce ntrations of FSH-regulatory peptides accompany the onset of puberty.