Beyond stimulating growth hormone, ghrelin influences the stress hormone axis, prolactin, thyroid function, and reproductive hormones, with special clinical significance in Cushing's disease.
4 hormonal axes beyond growth hormoneGhrelin influences the HPA/stress axis, prolactin, thyroid regulation, and reproductive hormone secretion
What the researchers found
Ghrelin influences multiple neuroendocrine axes: (1) It stimulates the HPA axis (stress response) independently of the pituitary, acting through the hypothalamus via CRH, AVP, and neuropeptide Y. (2) In ACTH-secreting tumors (Cushing's disease), pathological ghrelin receptor expression causes especially high ACTH and cortisol responses. (3) Ghrelin stimulates prolactin release from somatomammotroph cells. (4) Effects on thyroid axis regulation remain controversial. (5) Ghrelin inhibits FSH and especially LH secretion, likely through hypothalamic inhibition of GnRH.
Why it matters
Understanding ghrelin's broad hormonal effects is crucial as drugs targeting the ghrelin system are developed for obesity, cachexia, and growth hormone disorders. Unintended effects on stress hormones, fertility, and other systems could become side effects. The Cushing's disease connection also has diagnostic implications — ghrelin stimulation tests could help identify ACTH-secreting tumors.
How the study worked
This is a narrative review chapter summarizing published human and animal studies on ghrelin's neuroendocrine actions beyond growth hormone release, covering the HPA axis, prolactin, thyroid, and gonadal systems.
What this study cannot tell us
This is a 2013 review chapter, so it does not include the most recent decade of ghrelin research. The thyroid effects remain controversial even within the review. Much of the evidence for specific mechanisms comes from animal studies that may not fully translate to humans. Quantitative data on effect sizes for each hormonal axis are not provided in the abstract.
How to read the evidence
This is a narrative review chapter synthesizing evidence from multiple human and animal studies. While it provides a comprehensive overview, it does not include systematic methodology or quantitative analysis.
When this study was published
Published in 2013, this review captures the understanding of ghrelin's neuroendocrine actions as of a decade ago. Significant additional research has since expanded knowledge in several of these areas.
The bigger picture
The discovery that a single peptide hormone can coordinate multiple hormonal systems highlights the complexity of neuroendocrine regulation. Ghrelin's ability to simultaneously affect appetite, growth, stress, and reproduction positions it as a master integrator of nutritional status with reproductive and stress physiology — a concept important for understanding eating disorders, stress-related infertility, and metabolic syndrome.
Questions still open
- Could ghrelin receptor drugs developed for obesity or cachexia have unintended effects on fertility or stress hormones?
- Has ghrelin stimulation testing been further validated as a diagnostic tool for Cushing's disease since this review?
- Does the inhibitory effect on reproductive hormones explain the fertility problems seen in conditions with elevated ghrelin, like anorexia nervosa?
Common questions
Why does a hunger hormone affect so many other hormones?
What does this mean for Cushing's disease?
Read the original research
Other than growth hormone neuroendocrine actions of ghrelin.
Endocrine development, 25, 59-68
Citation
Benso, Andrea; Calvi, Elisa; Gramaglia, Elena; Olivetti, Ilaria; Tomelini, Michela; Ghigo, Ezio; Broglio, Fabio. (2013). Other than growth hormone neuroendocrine actions of ghrelin.. Endocrine development, 25, 59-68. https://doi.org/10.1159/000346054