It is common to see patients with severe and persistent hypocalcemia due to injury to the parathyroid glands after thyroid surgery, which often causes painful cramps and numbness in the hands and feet due to low calcium. However, there are still many patients who have symptoms despite daily calcium and vitamin D supplementation, and it seems that calcium supplementation for these patients is a matter of concern. First, let’s start with the role of the parathyroid glands. The parathyroid glands are located behind the thyroid gland in the neck. In some people, the parathyroid glands can grow inside the thyroid gland or in the rest of the neck due to congenital anatomical variation, which is called “vagal parathyroid glands”. The parathyroid glands mainly secrete parathyroid hormone (PTH), which is an important hormone that controls calcium and phosphorus metabolism in our body. Its main functions include promoting bone resorption, releasing calcium from bones into the blood, promoting urinary calcium reabsorption into the blood by the kidneys, activating vitamin D in the body to increase calcium absorption in the intestine and further reducing urinary calcium excretion. PTH maintains normal calcium and phosphorus metabolism in the body by increasing blood calcium. Secondly, what is happening in hypoparathyroid patients? In hypoparathyroid patients, PTH secretion by the parathyroid glands is reduced for a variety of reasons, causing the above mechanisms for raising blood calcium to be weakened or absent, resulting in the inability to release calcium from the bones into the blood on the one hand, and the kidneys converting blood calcium into urinary calcium and excreting it in the urine on the other. This leads to a series of symptoms such as cramps and numbness due to low calcium. It is important to note that in hypoparathyroidism patients, the main mechanism of low calcium is the blocked activation of vitamin D in the body due to the decrease of PTH. So now we can know how to supplement calcium in hypoparathyroid patients. The treatment of hypocalcemia in hypoparathyroid patients should be done with PTH drugs if the cause is the cause, but since PTH drugs are not yet available in China on the one hand, and PTH is a peptide hormone on the other hand, it is still troublesome and expensive to preserve, use and cost. Therefore, in most cases, we use symptomatic treatment, that is, calcium and vitamin D supplementation for treatment. In such a calcium supplementation treatment, due to the special hypoparathyroidism leading to low calcium principle, more emphasis is placed on adequate supplementation with vitamin D preparations. Generally speaking, 1000~2000mg of elemental calcium supplementation per day is sufficient for adults (it should be noted that this refers to elemental calcium, not the amount of calcium supplements, the content of elemental calcium in various calcium supplements varies, in the case of the most commonly used calcium carbonate, which contains 40% elemental calcium, that is to say, if you take 1000mg of calcium carbonate, the amount of elemental calcium supplementation is actually 400mg). For hypoparathyroid patients, the amount of vitamin D supplementation per day is more demanding, because of insufficient activation of vitamin D due to insufficient PTH in the body, therefore, active vitamin D preparations are generally used (commonly used are osteopontin and alfa osteopontin, both can be used), generally speaking, active vitamin D preparations for adults need to supplement 1~2μg per day. How can I control the amount of calcium and vitamin D supplementation? It is recommended to check blood calcium and phosphorus after taking calcium and vitamin D for 3-5 days, with a target of 2.1-2.3 mmol/L for calcium and 1.2-1.5 mmol/L for phosphorus. If the vitamin D supplementation is increased and the blood calcium reaches the target but the blood phosphorus is too high, then the amount of vitamin D supplementation can be reduced and the amount of calcium supplementation can be increased at the same time. This will gradually titrate the patient’s calcium and phosphorus in small steps to achieve therapeutic control goals.