▪Both vitamin D and parathormone (PTH) contribute to calcium (Ca) homeostasis. Vitamin D is responsible for the viability of the intestinal absorption of Ca, while PTH for maintaining Ca homeostasis in face of its deficiency. When serum Ca is at suboptimal concentrations, PTH stimulates Ca reabsorption from bone stores, and renal reabsorption, which could increase the risk of GDM, mediated by insulin resistance. The gene discussed is PTH; the disease is gestational diabetes.