Clinical Thyroidology® for the Public
Summaries for the Public from recent articles in Clinical Thyroidology
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THYROID SURGERY
Does thyroid surgery increase the risk of chronic kidney disease?
BACKGROUND
Thyroid surgery is recommended for the treatment of thyroid cancer and a variety of non-cancer thyroid diseases, including Graves’ disease and large and/or obstructive thyroid nodules and goiters. Thyroid surgery is safe with few complications, especially if the surgery is done by surgeons that do many thyroid operations annually. A potential complication of thyroid surgery is hypoparathyroidism caused by damage to the parathyroid glands causing hypocalcemia (low calcium levels). The parathyroid glands produce parathyroid hormone (PTH) that regulates calcium levels. PTH interacts with the bones, the kidneys and Vitamin D to regulate calcium levels. Because there are 4 total parathyroid glands (2 on each side of the thyroid), hypoparathyroidism is only seen after a total thyroidectomy. When it occurs, post-surgical hypoparathyroidism is usually mild and short-lived, usually resolving in 2-3 weeks.
Post-surgical permanent hypoparathyroidism is much more serious and is often difficult to treat. Further, treatment requires calcium levels to be maintained within a very narrow range. Permanent hypoparathyroidism has been associated with long-term problems, including an increased risk of heart and kidney disease as well as neurological problems. The most concerning risks of permanent hypoparathyroidism are related to kidney problems, including nephrocalcinosis (build up of calcium deposits in the kidney), kidney stones and chronic kidney disease (CKD).
This study was done to understand the risk of developing hypoparathyroidism and CKD after total thyroidectomy.
THE FULL ARTICLE TITLE
Reinke R, et al. Increased risk of chronic kidney disease after total thyroidectomy: a nationwide matched cohort study. J Clin Endocrinol Metab. Epub 2024 Aug 10:dgae534; doi: 10.1210/clinem/dgae534. PMID: 39126399.
SUMMARY OF THE STUDY
This study was conducted in Denmark. A review of patient charts from 1998-2017 was done using four nationwide Danish registries and a total of 2421 patients were identified who had undergone a total thyroidectomy. The study included patients > 18 years and who were not on a vitamin D supplement, calcium or had kidney disease before the surgery. They then assessed the long-term risk of developing CKD at 1, 5 and 10 years after surgery. Patients were matched with sex-matched individuals identified from the Danish Civil Registry System who had not had thyroid surgery and did not have CKD or hypoparathyroidism.
Of the patients who had undergone a thyroidectomy, 521(21.5%) were classified as having chronic hypoparathyroidism. The authors found the risk of CKD to be higher in those who underwent thyroid surgery despite their parathyroid status as compared to the control group that did not have thyroid surgery. At 10 years, the risk of CKD for patients who had hypoparathyroidism after thyroidectomy was 13.5%, as compared to 11.6% of the surgery patients with normal parathyroid function and 5.8% for the control group. Overall, the risk for development of CKD was 3.23 x the non-surgery group for the hypoparathyroid patients and 2.23 x the non-surgery group for patients with normal parathyroid function. Overall, patients who underwent thyroidectomy for hyperthyroidism had the highest risk for developing CKD, 4.59 x the non-surgery group.
WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study suggests that patients who undergo total thyroidectomy may be at a higher risk for developing CKD if they develop hypoparathyroidism after the surgery or had the surgery for hyperthyroidism. More clinical studies that assess this correlation further would be needed to understand the long-term impact of thyroidectomy on developing the postoperative complication of CKD and the underlying reasons that may increase the patient’s risk of developing this complication. It would also be important to evaluate the risk of developing CKD after thyroid surgery done by high volume thyroid surgeons, in whom the risk of permanent hypoparathyroidism is markedly less (~1%) than seen in this study.
— Vibhavasu Sharma, MD
ATA RESOURCES
Hyperthyroidism (Overactive): https://www.thyroid.org/hyperthyroidism/
Thyroid Surgery: https://www.thyroid.org/thyroid-surgery/
ABBREVIATIONS & DEFINITIONS
Thyroidectomy: surgery to remove the entire thyroid gland. When the entire thyroid is removed it is termed a total thyroidectomy. When less is removed, such as in removal of a lobe, it is termed a partial thyroidectomy or a lobectomy.
Hypocalcemia: low calcium levels in the blood, a complication from thyroid surgery that is usually shortterm and relatively easily treated with calcium pills. If left untreated, low calcium may be associated with muscle twitching or cramping and, if severe, can cause seizures and/or heart problems.
Parathyroid glands: usually four small glands located around the thyroid that secrete parathyroid hormone (PTH) which regulates the body’s calcium levels.
Parathyroid hormone (PTH): the hormone that regulates the body’s calcium levels. High levels of PTH cause hypercalcemia, or too much calcium in the blood. Low levels of PTH cause hypocalcemia, or too little calcium in the blood.
Hypoparathyroidism: low calcium levels due to decreased secretion of parathyroid hormone (PTH) from the parathyroid glands next to the thyroid. This can occur as a result of damage to the glands during thyroid surgery and usually resolves. This may also occur as a result of autoimmune destruction of the glands, in which case it is usually permanent.
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