Hyperactivity aggravates semistarvation-induced changes in corticosterone and triiodothyronine concentrations in plasma but not luteinizing hormone and testosterone levels.

Semistarvation over a ten-day period resulted in a weight loss of 30% in male Wistar rats, which had continuous access to a running wheel. The animals increased their activity up to 20 km per day. Controls fed ad lib increased activity only slightly (up to 2.3 km on day ten). Groups of semistarved and ad lib-fed sedentary rats were studied as controls. The circadian pattern of corticosterone (B), triiodothyronine (T3), luteinizing hormone (LH) and testosterone (T) was studied. Corticosterone was synergistically increased by semistarvation and exercise. The reduction of triiodothyronine by semistarvation was significantly greater in the running wheel group. Both luteinizing hormone and testosterone were significantly decreased by semistarvation. Hyperactivity did not result in additional suppression of LH and testosterone.