First Latin America Hypoparathyroidism Study Finds Poor Disease Control

People with hypoparathyroidism in Argentina, particularly those with kidney problems and high levels of phosphate in the blood, frequently experience inadequate disease control, a study found.

The study is the first to analyze hypoparathyroidism in Latin America, researchers said.

Titled “Hipopara-Red, Real Life Experience in 322 Patients with Hypoparathyroidism,” the study was published in the Journal of the Endocrine Society.

Hypoparathyroidism is caused by the insufficient activity of the parathyroid glands, located in the neck. These glands make the parathyroid hormone (PTH), which is important for regulating a variety of bodily functions, including calcium levels. Most of the well-defined symptoms of hypoparathyroidism — such as muscle cramps, fatigue, and brittle nails — are attributable to abnormally low body calcium levels. Consistently, treatment for the condition generally aims to increase the levels of calcium, while also looking to keep blood phosphate and magnesium levels within the normal range.

Since hypoparathyroidism is a rare condition, data on how it tends to manifest and progress are scarce — and this lack of data makes it difficult to know how best to manage the disorder in clinical practice.

Aiming to add to the available data, a team of researchers from Buenos Aires reported on information and records from 322 hypoparathyroidism patients treated at more than a half-dozen specialized centers in Argentina between 1985 and 2018.

“Our primary endpoint [goal] was to describe the natural history and clinical characteristics of a group of patients with hypoparathyroidism from 7 referral bone centers in Argentina,” the scientists wrote.

Most of the patients (85.7 %) were women, with a mean age at diagnosis of 43.8 and a median disease duration of 10.9 years. The mean age at the participants’ most recent healthcare visit was 55.2 years. Notably, most of the individuals were being treated with calcium supplements, often in addition to vitamin D supplements and/or diuretics.

In about 90% of the patients, hypoparathyroidism occurred as a result of surgery. Notably, surgery in which the parathyroid glands are damaged is a main cause of the condition. Most surgeries were performed due to cancers, the most common type being thyroid cancer.

A subsequent analysis found that the occurrence of hypoparathyroidism after surgery has decreased in recent years: prior to 2010, 49.6% of patients undergoing a certain type of thyroid surgery developed hypoparathyroidism; after that, the rate decreased to 37.2%.

In comparisons among the patients, those with non-surgical hypoparathyroidism were younger at diagnosis. This group showed a more even split between men and women. According to the researchers, these differences were expected and are in agreement with previously published data.

Of the analyzed patients, 31.3% experienced paresthesia, or pins-and-needles sensations, while 13.3% had muscle spasms and 14.2% had tetany, or muscle cramps and contractions. Just over a quarter (83 people; 25.7%) had a history of severe hypocalcemia or low body calcium levels that required hospitalization, while 14 patients (4.3 %) had a history of seizures.

According to available data from laboratory tests, 42.1 % of patients had higher-than-normal levels of phosphate, which, like calcium, is regulated by PTH. High phosphate levels can exacerbate kidney problems.

“Unfortunately, in our patients, lowering serum [blood] phosphate seems to be one of the most challenging tasks,” the investigators wrote.

In addition, many patients had evidence of kidney impairment, which was particularly common in older individuals.

“We were surprised and worried about the high percentage of patients with inadequate control, especially patients with hyperphosphatemia [high phosphate levels] and renal complications,” the researchers wrote.

Natpara, marketed by Takeda Pharmaceuticals, is a PTH replacement therapy approved for the treatment of hypoparathyroidism in the U.S. Based on international guidelines, the team determined that 210 of the patients (65%) met criteria for considering the use of this treatment, which is not yet commercially available in Argentina.

Limitations of this study include its retrospective nature and the fact that only centers that treat adults were included — which likely contributed to the high frequency of surgical hypoparathyroidism, according to the scientists.

“That being said, our results were generally consistent with peer‐reviewed reports,” the researchers wrote.

“In addition, according to our knowledge, this is the first study on hypoparathyroidism in Argentina and Latin America,” the team wrote, adding that the strengths of the analysis were the large number of patients included, its lengthy follow-up period, and the complete biochemical profiles examined.

According to other researchers, including those behind a June 2020 study in Columbia, data on hypoparathyroidism in Latin America is limited.

“Being aware of our current management of this rare disease is the first step to improve our clinical approach in the future,” the researchers here concluded.