Secondary hyperparathyroidism. Secondary hyperparathyroidism is the result of another condition that lowers calcium levels. This causes your parathyroid glands to overwork to compensate for the calcium loss. Factors that may contribute to secondary hyperparathyroidism include: Severe calcium deficiency.
https://www.mayoclinic.org/diseases-conditions/hyperparathyroidism/symptoms-causes/syc-20356194

