PMID: 107814Apr 1, 1979

Hypothalamus-pituitary-thyroid axis interactions with pineal gland in the rat

The American Journal of Physiology
G L BrammerJ M Hershman


We examined in the rat several possible relationships between the pineal gland and the hypothalamus-pituitary-thyroid axis. The pineal gland, the retina, and the hypothalamus exhibited a diurnal rhythm in thyrotropin-releasing hormone (TRH) content with peak values occurring around 1200 h. This rhythm in the hypothalamus was abolished by constant light but was not affected by pinealectomy. Nor did pinealectomy affect hypothalamic TRH content, pituitary content of thyroid-stimulating hormone (TSH) or prolactin; serum levels of (TSH), triiodothyronine (T3), or thyroxine (T4), or serum free-thyroxine index; or free-triiodothyronine index. Melatonin did not affect TSH or prolactin release from the anterior pituitary or TRH release from the hypothalamus in vitro. Isoproterenol did not affect the TRH content of pineal glands in vitro; nor did TRH or T3 affect basal or stimulated activities of serotonin N-acetyltransferase, the presumed controlling enzyme in melatonin production. We found no evidence for significant interactions between the pineal gland and the hypothalamus-pituitary-thyroid axis.

Related Concepts

Circadian Rhythms
Hypothalamo-Hypophyseal System
Pineal Gland
Thyroid Gland
Proterelin Tartrate Hydrate
Culture Techniques

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