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Postnatal maturation patterns of serum corticosterone and growth hormone in rats: effect of chronic thyroxine
Insights
Neonatal hyperthyroidism in rats, induced by thyroxine (T4), alters serum corticosterone and growth hormone (GH) levels during development. Chronic T4 exposure impacts hormone patterns under both basal and stress conditions.
Area of Science:
- Endocrinology
- Developmental Biology
- Pharmacology
Background:
- Neonatal thyroid hormone levels are critical for normal development.
- Thyroid hormones influence the hypothalamic-pituitary-adrenal (HPA) axis and growth hormone (GH) secretion.
- Disruptions in thyroid function during the neonatal period can have long-lasting effects.
Purpose of the Study:
- To investigate the impact of chronic neonatal hyperthyroidism on the ontogeny of serum corticosterone and GH in rats.
- To assess hormonal responses under both basal and stress conditions.
Main Methods:
- Rat pups were administered daily thyroxine (T4) or saline (control) from birth.
- Serum corticosterone and GH levels were measured at various time points.
- Hormonal levels were assessed under basal conditions and following a stress stimulus.
Main Results:
- Chronic T4 administration led to sustained elevated basal corticosterone levels by day 12.
- T4 treatment significantly increased serum corticosterone in response to stress by day 4.
- Serum GH levels were decreased in T4-treated rats compared to controls, with a more pronounced reduction under stress.
Conclusions:
- Chronic neonatal hyperthyroidism significantly alters the developmental trajectories of serum corticosterone and GH in rats.
- Thyroxine exposure during the neonatal period influences the HPA axis and GH regulation in a dose- and condition-dependent manner.
- These findings highlight the sensitivity of the developing endocrine system to thyroid hormone perturbations.
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 micrograms/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.