Hormonal Changes in Burned Hamsters

The Syrian (golden) hamster has provided the most extensively studied model of pineal physiology, and in the species the pineal gland has a potent suppressive effect on the reproductive system and on serum free thyroxim (T4) concentration. The pineal's suppressive effect on the gonads and T4 is classically evoked by subjecting the hamsters to a short photoperiod (less than 12-h light/day) or to blinding by bilateral orbital enucleation. Additional pinealectomy prevents the regression of the reproductive system and the reduction of T4. Burn injury of humans results in depressed serum concentrations of free triiodothyroxine (T3) and T4, reduced serum binding of T4, and low testosterone concentrations. Burned male Syrian hamsters (burn size 23% of body surface) exhibited reduced total (T4) and free (FT4) serum concentrations, a defect in T4 binding to serum proteins manifested by the T4 dialyzable fraction but not the in vitro T3 charcoal uptake, and reduced serum testosterone concentration. These changes are similar to those noted previously in burned humans. Unlike such patients, burned hamsters did not exhibit reduced serum T3 nor elevated rT3 concentrations in a reproducible manner. Pinealectomy performed before burning in hamsters did not prevent the burn-induced depression in serum T4 and testosterone.