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Thyrotropic hormone and thyroidal function initiation in fetal rat.
Journal of Developmental Physiology
|June 1, 1985
Summary
Thyroid-stimulating hormone (TSH) in fetal rats peaks on day 18, coinciding with increased cAMP. This suggests TSH plays a key role in early rat thyroid development and function.
Area of Science:
- Endocrinology
- Developmental Biology
- Molecular Biology
Background:
- Thyroid-stimulating hormone (TSH) is crucial for thyroid hormone production.
- Understanding the developmental role of TSH in fetal mammals is essential.
Purpose of the Study:
- To investigate the temporal dynamics of TSH and thyroxine (T4) in developing rat fetuses.
- To explore the relationship between TSH and cyclic adenosine monophosphate (cAMP) in the fetal rat thyroid.
Main Methods:
- Quantification of TSH and T4 levels in fetal rat plasma at different gestational ages (day 16, 18, 21).
- Measurement of cAMP concentrations in fetal rat thyroid tissue.
- In vitro stimulation of cAMP accumulation in fetal rat thyroid explants by TSH.
Main Results:
- TSH was detected from day 16, peaking on day 18, and decreasing by day 21.
- Thyroxine (T4) was detected from day 18, with levels increasing by day 21, suggesting negative feedback on TSH.
- Elevated plasma TSH levels correlated with high thyroid cAMP concentrations, and TSH stimulated cAMP accumulation in vitro.
Conclusions:
- TSH plays a significant role in the developing rat thyroid gland.
- The TSH-cAMP pathway is active in the fetal rat thyroid, indicating a functional role for TSH in development.
- Findings suggest a mechanism for TSH regulation involving negative feedback by T4.