Review: Genetic and physiological regulators of parathyroid hormone and the vitamin D system in pigs

Calcium and phosphorus are essential for skeletal mineralisation and metabolism in mammals including pigs. Endogenous regulatory processes ensure a balance in mineral absorption, utilisation, retention, and excretion. Mineral homeostasis is maintained through a network of hormones and responsive loci that interact via direct effects and feedback regulation at both systemic and tissue-specific levels. The regulation of important endocrine factors such as parathyroid hormone (PTH) and vitamin D metabolites, as well as other regulators like fibroblast growth factor 23 (FGF23), is also significant in pigs. This review presents physiological and genetic findings on mineral homeostasis in pigs and contributes to a comprehensive understanding of mineral biology in monogastric animals by highlighting the current state of knowledge and functional targets. It examines molecular processes related to (i) the regulation of PTH within the parathyroid glands and (ii) the physiological, tissue-specific activation of the vitamin D system. Investigations of (iii) the natural genetic variability of mineral balance in pigs complement findings on physiology and on responses to exogenous factors, such as dietary mineral supply and exposure to UV-B radiation. The endogenous activation of the vitamin D system is considered of particular value to promote mineral utilisation, bone health, and immunity across divergent management types in pig husbandry. Overall, the review highlights how research on PTH and the vitamin D system can contribute to maintaining pig health and supporting the sustainable use of mineral phosphorus resources in the long-term.