Why Sheep Are a Good Model Early play and social behaviors differ between sexesEarly play and social behaviors differ between sexes Juvenile/adult social behaviors differ between sexesJuvenile/adult social behaviors differ between sexes Reproductive behaviors differ between sexesReproductive behaviors differ between sexes

MASCULINIZATION DEFEMINIZATION Postnatal 1.timing of pubertal increase in GnRH secretion 2. function of GnRH surge system conception STEROIDS ORGANIZE FEEDBACK CONTROL OF GnRH SECRETION days of pregnancy birth Sheep Critical Period

Treatment Pregnant females injected with testosterone or oil vehicle during 2 nd trimester from days of gestationPregnant females injected with testosterone or oil vehicle during 2 nd trimester from days of gestation Groups:Groups: –30-90 days of oil [CM and CF] –30-90 days of TP (100 mg 2x/week) [TM and TF] –60-90 days of TP (100 mg 2x/week) [F only]

Physiological Consequences TP at both durations causes fetal growth retardation in both sexes (weight, height and chest circumference)TP at both durations causes fetal growth retardation in both sexes (weight, height and chest circumference) Mannikam, et al, Endocrinology, 2004 TP for 30-90, but not days, alters external genitalia in both sexesTP for 30-90, but not days, alters external genitalia in both sexes TP at both durations causes male urination pattern in femalesTP at both durations causes male urination pattern in females

Growth Curves

Testosterone Levels

Mannikam, et al, Endocrinology, 2004 External Genitalia