Abstract
Plasma T4, T3, and TSH, and total and 131l-labeled T4 and T3 in thyroid digests were determined in male and female rats from birth to 30–45 days postnatally. Mothers and offspring were fed a high-iodine Purina diet throughout. In both sexes, plasma T4 was<1 μg/100ml at birth but rose linearly to a peak of 6–7 μg/100 ml at day 15. Plasma T3 remained low at 30–40 ng/100 ml until day 10, then rose steeply to 80–100 ng/100 ml at day 20–30. Plasma TSH had a bimodal distribution with an early peak in the intial 1–2 weeks of life and a second rise after day 30. Adult pattern sex differences in plasma TSH appeared by day 30. Labeled T3 was u ndetectable i n thyroid digests until after day 7. Both labeled and stable T3 and T4 concentration and T3/T4 ratios rose progressively during the first 2 weeks of life. After day 7, stable and labeled intrathyroidal T3/T4 ratios were significantly correlated, but the latter was always higher than the former for any given age.
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Supported by grants from the NIAMDD, National Institutes of Health, Bethesda Maryland.
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Fukuda, H., Greer, M.A. Postnatal development of pituitary-thyroid function in male and female rats: comparison of plasma and thyroid T3 and T4 concentration. J Endocrinol Invest 1, 311–314 (1978). https://doi.org/10.1007/BF03350975
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DOI: https://doi.org/10.1007/BF03350975