SERUM BIOACTIVE LUTEINIZING AND FOLLICLE-STIMULATING-HORMONE CONCENTRATIONS IN GIRLS INCREASE DURING PUBERTY

FSH plays an essential role in folliculogenesis and ovarian growth. Ho wever, cross-sectional studies have not shown an increase in bioactive FSH (B-FSH) during puberty. To eliminate intersubject variability, we used a longitudinal design and tested the hypothesis that B-FSH incre ases during puberty. Thirty normal, healthy girls were enrolled in a l ongitudinal study from pubertal stages I to IV. The subjects were eval uated at 6-mo intervals; each visit consisted of pubertal staging, bon e age determination by x-ray, measurements of serum immunoreactive FSH (I-FSH) and B-FSH (n = 14) or immunoreactive LH (I-LH) and bioactive LH (B-LH) (n = 18), and adrenal and ovarian steroids. All girls had cl inical and hormonal characteristics of puberty. Both I-FSH and B-FSH l evels were relatively elevated before puberty, whereas serum I-LH and B-LH were low. From pubertal stages I to III, there was a modest yet s ignificant rise in serum I-FSH (p < 0.001) and serum B-FSH (p < 0.01). Serum I-LH and B-LH concentrations showed the expected increases with puberty (p < 0.001), with serum B-LH concentrations exhibiting a grea ter rise than I-LH (p < 0.001). Our results demonstrate that serum B-F SH and I-FSH increase during puberty. Relatively elevated B-FSH concen trations from early to midpuberty may be an important factor for ovari an growth while circulating LH and estrogen are still low. As puberty progresses, the continued and selective increase in LH induces a rise in estradiol and ultimately leads to ovulation.