From the Guidelines
Thyrotropin-releasing hormone (TRH) is a crucial hormone that stimulates the pituitary gland to release thyroid-stimulating hormone (TSH), regulating thyroid function and overall metabolism. As noted in the study by Fischer et al. 1, the hypothalamic-pituitary-thyroid (HPT) axis plays a significant role in various bodily functions, including mood regulation and anxiety disorders. The study found that nearly all included studies showed a significant comorbidity between anxiety and thyroid disorders, highlighting the importance of thyroid function in mental health. Some key points about TRH include:
- It is a small peptide hormone produced by the hypothalamus
- It stimulates the pituitary gland to release TSH, which in turn regulates the production of thyroid hormones (T3 and T4) by the thyroid gland
- Abnormal TRH or TSH responses can be indicative of thyroid or pituitary disorders, as observed in the TRH stimulation test
- TRH has effects beyond thyroid regulation, including influences on mood, energy levels, and autonomic functions, as discussed in the context of anxiety disorders by Fischer et al. 1. The findings of Fischer et al. 1 support the clinical recommendation to routinely screen for thyroid disorders in patients with anxiety disorders, underscoring the complex interplay between thyroid function and mental health.
From the FDA Drug Label
Thyrotropin releasing hormone (TRH) released from the hypothalamus stimulates secretion of thyrotropin stimulating hormone (TSH) from the anterior pituitary. Thyrotropin-Releasing Hormone (TRH) is a hormone that stimulates the secretion of Thyrotropin-Stimulating Hormone (TSH) from the anterior pituitary, which in turn regulates the synthesis and secretion of thyroid hormones. The main points are:
- TRH is released from the hypothalamus.
- TRH stimulates the secretion of TSH.
- TSH regulates the synthesis and secretion of thyroid hormones 2
From the Research
Definition and Function of Thyrotropin-Releasing Hormone (TRH)
- Thyrotropin-releasing hormone (TRH) is a tripeptide hormone produced in the hypothalamic paraventricular nucleus (PVN) 3.
- TRH is the main positive regulator of thyrotropin (TSH) secretion, and its action is integrated with the negative feedback of thyroid hormone to guarantee appropriate thyroid stimulation 4.
- TRH affects various steps of the biosynthetic process within thyrotrophs, with major effects on the posttranslational maturation of TSH oligosaccharide chains, and is necessary for the secretion of the glycoprotein hormone with full biological activity 4.
Regulation of TRH Production and Release
- TRH synthesis and release are regulated by multiple pathways, including feedback from thyroid hormone and energy expenditure 5.
- TRH production is regulated directly at the transcriptional level by leptin, one of the adipocytokines that plays a critical role in feeding and energy expenditure 6.
- Destruction of the PVN reduces TRH and TSH secretion dramatically, while electrical stimulation of this nucleus enhances their release 3.
Role of TRH in Energy Homeostasis and Thyroid Function
- TRH controls energy homeostasis mainly through its hypophysiotropic actions to regulate circulating thyroid hormone levels 6.
- TRH neurons in the PVN are major regulators of the hypothalamic-pituitary-thyroid (HPT) axis and the fasting-induced suppression of TH levels 7.
- Activation of TRH neurons leads to increased TSH and TH levels, demonstrating the specific role of PVN TRH neurons in the regulation of the HPT axis 7.