Abstract
We examined the consequences of neonatal hyperthyroidism on somatic growth and SMG- and serum-EGF levels in one month old female mice. Littermate pups were randomly divided into control (vehicle injected) and thyroxine (T4) treated (0.4 ug/g BW/day) groups. Animals were treated with vehicle or T4 from birth (day 0) through day 6 and sacrificed on day 31. T4 treatment resulted in acceleration of both tooth eruption and eyelid opening, and in addition, caused growth retardation (Body weight: control vs T4-treated 22.3±0.5g and 16.0±0.8g P<0.001; and nose to rump length: control vs T4-treated (cm) 9.3±0.1 and 8.2±0.1 P<0.001). SMG and serum EGF concentrations were measured by RIA with results as follows: T4 treatment inhibited the normal ontogenic rise in SMG-EGF and increased serum EGF levels. Conclusion: Neonatal hyperthyroidism accelerates maturation but inhibits growth. Speculation: This may be due to augmented tissue EGF production while SMG maturation is impaired.
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