Characterization of estrogens, testosterone, and cortisol in normal bottlenose dolphin (Tursiops truncatus) pregnancy

• E1/E1-C and E3 predominant estrogens in bottlenose dolphin serum according to HPLC.
• E1-C increased in LATE pregnancy and was affected by parity and age.
• E3 was highest in EARLY pregnancy.
• T increased throughout pregnancy.
• CORT was highest in LATE pregnancy.

The goal of this study was to describe profiles of serum estrogens, testosterone and cortisol during normal pregnancy in bottlenose dolphins. Predominant estrogens in all categories of dolphin sera pools during estrus and pregnancy (EARLY: Days 0–120; MID: Days 121–240; LATE: Days 241 to parturition; Day 0 = day of conception) were estrone/estrone conjugates (E1-C) and estriol (E3). Serum samples collected throughout 101 normal pregnancies were analyzed for E1-C, E3, testosterone (T) and cortisol (CORT). E1-C was higher (P < 0.05) during LATE compared to EARLY and MID, and higher (P < 0.05) in nulliparous than multiparous females. E1-C concentrations were also inversely associated with maternal age (P = 0.05). E3 was higher (P < 0.05) in EARLY than MID and LATE, and higher overall for nulliparous than multiparous females, but concentrations were similar among gestational stages when parity was excluded from analyses. Analysis by indexed month post-conception (IMPC) demonstrated that E1-C increased from IMPC 9 and peaked at IMPC 11. E3 was significantly elevated during IMPC 1, decreased until IMPC 6 and peaked at IMPC 11. T increased (P < 0.05) at IMPC 3 and continued to increase throughout gestation (P < 0.05). CORT was higher (P < 0.05) during LATE compared to EARLY and MID (P < 0.05), peaked during IMPC 12, and was not affected by parity. Hormone profiles were not influenced by fetal sex.