From the Guidelines
Yes, Growth Hormone-Releasing Hormone (GHRH) is a tropic hormone. GHRH is produced by the hypothalamus and acts on the anterior pituitary gland to stimulate the synthesis and release of growth hormone (GH) [ 1, 1 ]. This makes it a tropic hormone by definition, as tropic hormones are those that specifically target endocrine glands to regulate their function and hormone production. GHRH follows the classic pattern of the hypothalamic-pituitary axis, where it serves as a regulatory signal in the endocrine cascade. When released in a pulsatile manner, GHRH binds to specific receptors on somatotroph cells in the anterior pituitary, activating intracellular signaling pathways that lead to increased growth hormone production and secretion 1.
Key Points
- GHRH is a hormone produced by the hypothalamus
- It acts on the anterior pituitary gland to stimulate GH release
- GHRH is a tropic hormone due to its specific action on the pituitary gland
- It plays a crucial role in the regulation of growth hormone production and secretion
The relationship between GHRH and GH exemplifies the hierarchical control system of the endocrine system, where one hormone (GHRH) controls the release of another hormone (GH), which then goes on to affect multiple target tissues throughout the body 1. This highlights the importance of GHRH in regulating growth and development, and its dysregulation can lead to conditions such as acromegaly 1.
From the Research
Definition of Tropic Hormones
- Tropic hormones are hormones that stimulate the secretion of other hormones from endocrine glands.
- They play a crucial role in regulating various physiological processes in the body.
Role of Growth Hormone-Releasing Hormone (GHRH)
- GHRH is a hypothalamic neuropeptide that stimulates the synthesis and secretion of growth hormone (GH) from the anterior pituitary gland 2.
- It is a key regulator of GH secretion and plays a vital role in growth and development 3, 4.
- GHRH has also been shown to have extrapituitary effects, including stimulation of cell proliferation, survival, and differentiation, and inhibition of apoptosis 4.
Classification of GHRH as a Tropic Hormone
- Based on its role in stimulating the secretion of GH from the anterior pituitary gland, GHRH can be classified as a tropic hormone 2.
- Its primary function is to regulate the secretion of another hormone (GH), which is a characteristic of tropic hormones.
- The molecular characterization of GHRH and its receptor (GHRH-R) has also been studied in various species, including fish, and has been shown to stimulate GH synthesis and release 5.
Summary of GHRH's Tropic Hormone Function
- GHRH is a tropic hormone that stimulates the secretion of GH from the anterior pituitary gland.
- It plays a crucial role in regulating growth and development, and has extrapituitary effects on various physiological processes.
- The classification of GHRH as a tropic hormone is supported by its role in regulating the secretion of another hormone (GH) and its molecular characterization in various species 3, 4, 2, 5.