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[Course of thyroxinemia during the development of the chick embryo. Influence of hypophysectomy]
Comptes Rendus Hebdomadaires Des Seances De L'Academie Des Sciences. Serie D: Sciences Naturelles
|November 8, 1976
Insights
Thyroxine (T4) is present in chick embryos by day 10. Pituitary control of thyroid hormone secretion begins after day 10, as shown by decreased T4 levels in hypophysectomized embryos.
Area of Science:
- Developmental biology
- Endocrinology
- Thyroid hormone research
Context:
- Investigating thyroid hormone dynamics in developing chick embryos.
- Examining the role of the pituitary gland in thyroid regulation during embryogenesis.
Purpose:
- To quantify plasma thyroxine (T4) levels in intact and hypophysectomized chick embryos from day 10 to 18 of incubation.
- To determine the onset of pituitary control over thyroid hormone secretion in avian embryos.
Summary:
- Plasma thyroxine (T4) levels were measured in chick embryos throughout incubation.
- T4 was detectable by day 10, increasing in controls until day 17.
- Hypophysectomy led to decreased T4 levels starting from day 11, indicating post-day 10 pituitary influence on thyroid function.
Impact:
- Provides insights into the developmental timeline of thyroid hormone regulation in chick embryos.
- Establishes the critical window for pituitary control of thyroid secretion in avian development.
- Contributes to understanding the interplay between the pituitary and thyroid axes during embryonic development.
Abstract:
Plasma thyroxine (T4) level of intact and hypophysectomized Chick embryos has been determined for the incubation interval 10 to 18 days. T4, which is the main circulating thyroid hormone, exists as early as day 10. The plasma T4 level of controls increases as power function of time from day 10 to day 17. Hypophysectomy (on day 2) produces a decrease of the plasma T4 level, but only from day 11, which accounts for the beginning of a pituitary control of the thyroid secretion after day 10.