Understanding the Link Between Acidity and Parathyroid Function

Managing mineral metabolism remains a significant challenge in chronic kidney disease (CKD). Recent research has uncovered a pivotal role for the OGR1 receptor PTH secretion mechanism in responding to extracellular acidity. While clinicians have long observed that metabolic acidosis exacerbates secondary hyperparathyroidism, the precise molecular sensors remained elusive until now. By utilizing 5-aminolevulinic acid to isolate parathyroid glands, scientists have demonstrated that acidic environments directly stimulate the release of parathyroid hormone (PTH).

The Role of OGR1 Receptor PTH Secretion in Acidosis

The ovarian cancer G protein-coupled receptor 1 (OGR1), also known as GPR68, acts as the primary proton sensor in the parathyroid gland. In wild-type models, decreasing the extracellular pH leads to a significant increase in PTH secretion. Conversely, parathyroid glands lacking the OGR1 receptor fail to mount this response. This indicates that OGR1 is indispensable for the pH-dependent regulation of PTH. Furthermore, the study suggests that no other proton-sensing receptors compensate for its absence, making it a highly specific target.

Additionally, the research highlights a synergistic interaction between calcium and pH signaling. Low extracellular calcium levels not only stimulate PTH directly but also promote local acidification. This local drop in pH further activates the OGR1 receptor PTH secretion pathway. This dual stimulation significantly enhances hormone release. Notably, this synergy is markedly diminished in OGR1-deficient glands, confirming the receptor's central role in integrating these signals.

Clinical Implications for CKD and Secondary Hyperparathyroidism

These findings provide a mechanistic bridge between metabolic acidosis and the progression of secondary hyperparathyroidism. In patients with CKD, the inability to excrete acid leads to chronic systemic acidosis. Consequently, this persistent acidic state may continuously drive PTH secretion via OGR1, independent of calcium levels. Therefore, targeting OGR1 signaling could offer a novel therapeutic avenue to control hyperparathyroidism without the side effects associated with traditional treatments.

Frequently Asked Questions

What is the OGR1 receptor?

OGR1, or GPR68, is a G protein-coupled receptor that senses changes in extracellular proton concentration. It translates acidic pH into intracellular signals that regulate various physiological processes, including hormone secretion.

How does acidosis affect PTH secretion?

Acidosis directly stimulates the parathyroid glands to release more PTH. This occurs through the activation of the OGR1 receptor, which detects the increased concentration of protons in the extracellular fluid.

Why is this discovery important for chronic kidney disease (CKD)?

Patients with CKD often suffer from metabolic acidosis and secondary hyperparathyroidism. Understanding that OGR1 mediates the acid-induced rise in PTH helps explain why acidosis worsens bone and mineral disorders in these patients.

Disclaimer: This content is for informational and educational purposes only. It does not constitute medical advice or establish a doctor-patient relationship. Always seek the advice of a qualified healthcare provider regarding a medical condition. Refer to the latest local and national guidelines for clinical practice.

References

• Yang Y et al. Acidic extracellular pH-induced PTH secretion in male mouse parathyroids is OGR1-dependent. Endocrinology. 2026 May 06. doi: undefined. PMID: 42089253.


• Ward DT et al. Pathophysiologic changes in extracellular pH modulate parathyroid calcium-sensing receptor activity and secretion via a histidine-independent mechanism. J Am Soc Nephrol. 2015;26(9):2155-2164.


• Rodriguez M et al. Regulation of parathyroid function in chronic renal failure. J Nephrol. 2006;19(2):122-133.