SHERMAN, R.A.; PAGARIGAN, L.; NOREN, D.P.; ORTIZ, R.M.; ORTIZ, C.L.; TALAMANTES, F.; Univ. of California, Santa Cruz; Univ. of California, Santa Cruz; Univ. of California, Santa Cruz; Univ. of California, Santa Cruz; Univ. of California, Santa Cruz; Univ. of California, Santa Cruz: Reproductive hormone concentrations in fasting, postweaned northern elephant seal (Mirounga angustirostris) pups

Although neonatal development is generally associated with increased levels of circulating testosterone (T) and estradiol (E2), food deprivation may inhibit steroidogenesis. Therefore serum concentrations of T, E2, progesterone (P4) and luteinizing hormone (LH) were measured by either radioimmunoassay (P4, LH) or enzyme immunoassay (T, E2) to examine this potential paradox in fasting, postweaned northern elephant seal (Mirounga angustirostris) pups. Blood samples were obtained from 20 male and 20 female pups at both early (<1 wk postweaning) and late (6-8 wk postweaning) periods during their natural postweaning fast. T (early: 2.9 ± 0.4 ng/mL, late: 16 ± 2 ng/mL; p < 0.0001) and E2 (early: 42 ± 6 ng/mL, late: 67 ± 5 ng/mL; p < 0.01) concentrations increased while P4 (early: 2.5 ± 0.3 ng/mL, late: 2.1 ± 0.3 ng/mL) did not. In males, LH was increased (early: 46 ± 4 pg/mL, late: 65 ± 6 pg/mL; p=0.025), but not in females (early: 69 ± 9 pg/mL, late: 65 ± 6 pg/mL). Increased T and E2 may be important for the continued development of postweaned pups despite their fasting state.