Postnatal Maturation Patterns of Serum Corticosterone and Growth Hormone in Rats: Effect of Chronic Thyroxine Administration

Abstract

The effects of chronic neonatal hyperthyroidism in rats on the ontogenic pattern of serum corticosterone and growth hormone (GH) were studied. Thyroxine (T₄) treated and saline injected rat pups were sacrificed under basal and stress conditions. In comparison to saline control animals', daily T₄ administration (0.4 µg/gram body weight) produced a sustained elevation in basal corticosterone levels by day 12 and a significant elevation of serum corticosterone in response to stress by day 4. The serum GH levels in non-stressed animals were moderately decreased in response to T₄ administration as compared to saline injected animals with a greater reduction in GH measured in samples obtained from stressed animals. The results indicate that chronic T₄ administration influences the developmental pattern of serum corticosterone and GH under both non-stress and stress conditions.

Development - Hyperthyroidism - Thyroxine - Corticosterone - Growth Hormone - Rats