Physical changes associated with the onset of precocious puberty in rats after treatment with PMSG.

Body dimensions, composition, oxygen consumption and core temperature were measured in 2 groups of immature rats treated with PMSG. The first group weighed over 60 g on Day 27 of life and responded to PMSG treatment by ovulating; the second group weighed less than 60 g and did not ovulate after PMSG. Body composition, expressed as a percentage of body weight, was identical in the two groups, but growth rate, oxygen consumption and body temperature were all lower in the lighter animals. Oxygen consumption and body temperature were manipulated by altering temperature (i.e. 5, 22 and 30 degrees C) or by hyperphagia, and a positive correlation was found between body temperature and the occurrence of ovulation.