BACKGROUND
Thyroidectomy is surgery to remove the entire thyroid gland. Thyroidectomy is done for treatment of both thyroid cancer and non-cancer thyroid problems such as Graves’ disease and nodular goiter. While thyroidotomy is a safe and effective procedure, especially when done by experienced thyroid surgeons, there are potential complications. One of the complications of thyroidectomy is the development of low calcium levels after surgery, known as post-operative hypocalcemia. This low calcium often happens between 1-3 days after surgery and can occur in up to 1/3rd of patients. The parathyroid glands located next to the thyroid produce parathyroid hormone (PTH) that controls blood calcium levels. The cause of post-operative hypocalcemia is damage/bruising of the parathyroid glands during surgery leading to low PTH levels. Treatment of low calcium levels after surgery can include calcium pills and/or calcitriol, an active form of vitamin D.

Most of the time, post-operative hypocalcemia is mild to moderate (identified with blood tests, mild symptoms like numbness or tingling in fingers or lips or with abnormal twitching of muscles) and resolves in a few days. However, severe hypocalcemia can result in seizures, heart arrhythmias, mental status changes and often requires rehospitalization. Several methods have been suggested to treat patients after thyroid surgery. These include just waiting and watching patients for low calcium, treating all patients with standard doses of calcium and vitamin D after surgery or adjusting the dose for each patient. These run the risk of over-treating some patients and add to overall health care costs.

This study was done to evaluate a protocol that grouped patients according to their parathyroid hormone level after surgery to help predict which patients would benefit from supplemental calcium and vitamin D. This study used a parathyroid hormone level drawn 4 hours after surgery to guide calcium and vitamin D supplementations to see if this reduced the incidence of hypocalcemia and readmissions.

THE FULL ARTICLE TITLE
Chindris AM, et al. Hypocalcemia post total thyroidectomy: a ten-year, single institution experience with a parathyroid hormone-guided calcium and calcitriol supplementation protocol. Endocr Pract 2025;31(11):1399- 1406; doi: 10.1016/j.eprac.2025.07.003. PMID: 40633692.

SUMMARY OF THE STUDY
This is a study of 882 consecutive patients who had total thyroidectomies at a single institution between January 2008 and December 2022. They were split into two groups – 148 who were treated prior to using the protocol (pre-protocol group) and 734 who were treated according to the protocol (protocol group). Patients who had previous parathyroid disease, parathyroid or thyroid surgery, untreated vitamin D deficiency or a prior diagnosis of hyperparathyroidism were excluded.

The patients in the pre-protocol group were managed with Ca carbonate (400 mg elemental Ca/tablet) 1-2 tablets every 4-6 h as needed, based on the postoperative serum Ca levels and/or symptoms of hypocalcemia, at the discretion of their surgeon. Patients in the protocol group had a 4-hour post operative PTH drawn and were split into 3 groups according to their hypocalcemia risk: low (PTH >30 pg/mL), intermediate (PTH 15-30 pg/ mL), and high (PTH <15 pg/mL). Treatment was only calcium carbonate in low-risk group, calcium carbonate with low dose calcitriol in intermediate group and calcium carbonate with high dose calcitriol in high-risk group. Calcium levels were monitored weekly and if normal, doses of calcium and/or calcitriol gradually decreased. Hypocalcemia was defined as a serum calcium <8.0 mg/ dl within 30 days of surgery. They looked at how often hypocalcemia was noted and whether hospital readmission for hypocalcemia was required as well as risk factors for developing hypocalcemia.

Hypocalcemia occurred in 20.9% of the pre-protocol subjects and was decreased to 9.5% in post-protocol subjects. Within this latter group, there was a low incidence of hypocalcemia in the low and medium risk groups (2.3 and 2.6% respectively) compared with the high-risk group in which the PTH was <15 pg/mL (23.4%). Other factors that increased the risk of hypocalcemia were lymph node dissection, parathyroid glands that were located within the thyroid gland and worsening kidney function.

Management of hypocalcemia differed between groups, with 40.0% of protocol patients treated as inpatients, 21.4% as outpatients, and 38.6% managed over the phone, compared with 80.6%, 16.1%, and 3.2% in the pre-protocol group.

Hypercalcemia (high calcium levels due to increase calcium pills) developed in 82 patients in the protocol group within 30 days post thyroidectomy. Only one of these patients required hospitalization.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study reinforced the previous information that measuring the PTH levels 4-h after surgery was helpful to predict the risk of low calcium levels after thyroidectomy. Along with the PTH-guided calcium and calcitriol treatment protocol, this reduced the incidence of hypocalcemia and hospital readmissions.

This is important to patients as it allows selection of patients who are good candidates for same-day surgery with resultant increase in patient satisfaction, and reduction in morbidity and health care costs.

— Marjorie Safran, MD

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