Weight Loss Surgery May Present Problems for Hypoparathyroidism Patients, Report Asserts

People with hypoparathyroidism who wish to undergo weight-loss surgery should consider possible difficulties in maintaining calcium levels within a normal range before undergoing the procedure.

The case report with that finding, “The challenges of post-bariatric surgery hypocalcaemia in pre-existing hypoparathyroidism,” was published in the journal Endocrinology, Diabetes & Metabolism Case Reports.

Hypoparathyroidism is caused by low levels of parathyroid hormone (PTH) in the blood, which causes calcium levels in the blood to drop, a medical condition known as hypocalcemia.

Standard treatment for hypoparathyroidism usually is a combination of calcium supplements and calcitriol (the active form of vitamin D), which are absorbed in the gastrointestinal tract. Yet, the management of hypocalcemia in people who underwent weight-loss surgery or with deficient absorption in the gut is difficult.

Investigators in Australia recently described the case of a woman with hypoparathyroidism who underwent elective sleeve gastrectomy — a type of weight-loss surgery in which a large portion of the stomach is removed to limit food intake — and later experienced several complications.

The 46 year-old woman weighed 95 kg (about 209 pounds) — and had a body mass index (BMI) of 38.5 kg per square meter (kg/m²), which classified her as obese, by the time of surgery.

In addition to obesity, she had a history of psoriatic arthritis, for which she was being treated with multiple immunosuppressants; she also hypoparathyroidism, which she developed after undergoing thyroid removal surgery 20 years prior. Still, her hypoparathyroidism had been well-managed over the years with a long-term treatment regimen of oral calcium carbonate and calcitriol.

She underwent sleeve gastrectomy in November 2018, which was converted in an emergency gastric bypass — a type of weight-loss surgery in which surgeons create a small stomach pouch that is then attached directly to a portion of the small intestine — due to several stomach perforations.

The patient subsequently developed sepsis and was transferred to intensive care four days after surgery. At arrival, her calcium levels were low — 0.78 millimoles per litre (mmol/L); normal range is 1.11–1.28 mmol/L. She required continuous infusions of a solution of calcium gluconate to bring up her calcium levels to a normal level.

In three months she started receiving intravenous (into-the-vein) calcitriol, which allowed physicians to lower the frequency of her calcium gluconate infusions from five to three daily. During this time, she also required treatment with levothyroxine to maintain her thyroid-stimulating hormone levels within normal range.

“Maintaining normocalcaemia [normal calcium levels] was fraught with difficulties in a patient with pre-existing surgical hypoparathyroidism, where oral replacement was impossible,” the investigators wrote.

She remained in intensive care for six months, during which she had more than 20 abdominal surgeries and lost 14 kg (about 31 lbs).

After remaining in the hospital for more than eight months, she eventually recovered to the point where she was able to start taking her routine medications by mouth. She was discharged and instructed to continue taking calcitriol, as well as a higher dose of calcium supplements (1,200 mg twice daily), compared with the once-daily dose she took before having weight-loss surgery.

Her calcium levels remained within normal range until her fourth month of follow-up, when she weighed 71.8 kg (about 158 pounds) and had a BMI of 29 kg/m².

“We propose careful consideration be given before elective bariatric surgery in patients with pre-existing hypoparathyroidism due to potential difficulties in managing hypocalcaemia in the setting of impaired gastrointestinal absorption, which is exacerbated when complications occur,” the scientists wrote.

They also noted that, when approved in Australia, Natpara — an injectable form of PTH developed by Shire (now part of Takeda) — may significantly change the way these patients are managed following weight-loss surgery. Natpara is approved in the U.S. — and in Europe under the brand name Natpar — to treat hypocalcemia associated with hypoparathyroidism.