Organ weights and serum FSH concentrations in hpg mice after treatment with estradiol and/or rhFSH. Wet weight of paired testes (top), epididymides (second panel) and seminal vesicles (middle panel), and serum concentrations of FSH of male hpg mice as determined in the human FSH ELISA (fourth panel) and the rat RIA (bottom). Groups of mice were treated for 50 days with subcutaneous implants containing either cholesterol (chol) or 2% estradiol (E), and also daily treatment with vehicle, 1 or 5 U of recombinant human FSH (Gonal-F™). Values are group mean ± SEM, group sizes as indicated. *P < 0.05, **P < 0.01 and ***P < 0.001 vs group treated with cholesterol implants and vehicle; @P < 0.01 vs all other groups.