A 46-year-old woman who was previously healthy was diagnosed with papillary thyroid carcinoma and referred for total thyroidectomy with neck dissection. Shortly after the surgery, the patient developed headache, tingling, muscle cramps, and leg spasms.
On physical examination the patient’s blood pressure was 102/74 mm Hg and heart rate was 62 beats/min. While measuring blood pressure, the patient developed carpal spasm. The neck examination revealed a normally healing surgical wound with no evidence of inflammation or infection. Gentle tapping on the cheek near the mouth resulted in facial twitching.
Laboratory findings revealed low albumin-corrected calcium levels of 7.3 mg/dL (normal range 8.5 to 10.5 mg/L) with parathyroid hormone (PTH) at the low end of the normal range. In addition, phosphate level was 4.8 mg/dL (normal range 2.5 to 4.5 mg/dL) and magnesium and vitamin D levels were in the normal range.
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The most common cause of hypoparathyroidism is injury or removal of the parathyroid glands during anterior neck surgery.1,2 The incidence of hypoparathyroidism after anterior neck surgery is approximately 8%. In more than 70% of cases, the hypoparathyroidism is transient and will resolve within 6 months, while in the remaining cases it will be permanent.3
Postsurgical hypoparathyroidism is significantly less common when the surgery is performed by an experienced neck surgeon and is expected to develop in <2% of these patients. Risk factors for hypoparathyroidism include neck dissection (as in this case), repeat neck surgery, and inability to visualize the parathyroid glands during the operation.
The goal of treatment for hypoparathyroidism is serum calcium levels in the low end of the normal range, or slightly below that, while avoiding symptoms of hypocalcemia. This usually requires oral calcium and active vitamin D (calcitriol or alfacalcidiol), but in some cases, subcutaneous recombinant PTH treatment may be advised.1
There is a wide variation in the manifestations of hypocalcemia. The acute manifestations may include neuromuscular irritability (tetany), with perioral numbness, paresthesias of the hands and feet, muscle twitching, and cramps. In more severe cases, laryngospasm and seizures may develop.1 The classic physical findings due to latent tetany are Trousseau and Chvostek signs. However, other patients may be asymptomatic or present with nonspecific symptoms, such as fatigue, anxiety, or depression.
Serum calcium and albumin should be measured on the day of the neck surgery and the next morning, as well as before hospital discharge. Based on the results, oral calcium and active vitamin D should be given as first-line treatment. Intravenous calcium with oral calcitriol may be used in cases of acute hypocalcemia, even when no symptoms are present.
As postsurgical hypoparathyroidism is often transient, calcium and vitamin D supplements should be tapered slowly in the weeks following surgery. Most patients will be able to discontinue the supplements entirely. Recombinant PTH 1-84 is an option for patients with permanent hypoparathyroidism who cannot maintain stable serum and urinary calcium levels with supplements of calcium and vitamin D. The option may be considered if high doses of calcium or active vitamin D are required, renal complications are present, quality of life is poor, or in the presence of gastrointestinal malabsorption.1
The long-term treatment for hypoparathyroidism is frequently associated with hypercalciuria, nephrocalcinosis and nephrolithiasis, and renal insufficiency. Frequent monitoring (at least every 6 months) of serum calcium, phosphate, magnesium, 25-hydroxyvitamin D, and creatinine levels, as well as urinary calcium excretion, is essential to adjust treatment appropriately. After changes in calcium or active vitamin D, the blood tests should be repeated in 1 to 2 weeks.
1. Kahn AA, Koch C, Van Uum SHM, et al. Standards of care for hypoparathyroidism in adults: a Canadian and International Consensus. Eur J Endocrinol. 2019;180(3):1-22.
2. Orloff LA, Wiseman SM, Bernet VJ, et al. American Thyroid Association statement on postoperative hypoparathyroidism: diagnosis, prevention, and management in adults. Thyroid. 2018;28(7):830-841.
3. Clarke BL, Brown EM, Collins MT, et al. Epidemiology and diagnosis of hypoparathyroidism. 2016;101(6):2284-2299.