Calcium control may cut risk of kidney problems in children: Study
Nonsurgical hypoparathyroidism poses risk of complications later in life
Written by |
Children with hypoparathyroidism that is not a consequence of surgery may face a significant risk of kidney complications later in life, particularly calcium deposits and reduced function, but careful control of calcium and phosphate levels during treatment may help lower that risk, a long-term study in China found.
The study, “Risk factors of renal complications in childhood-onset non-surgical hypoparathyroidism: a long-term follow-up study,” was published in Endocrine.
Hypoparathyroidism is characterized by low levels of parathyroid hormone (PTH), which is produced by the parathyroid glands and helps regulate calcium and phosphorus levels in the body. Damage to the parathyroid glands during thyroid surgery is the most common cause of hypoparathyroidism.
Less frequently, the disease has nonsurgical causes, including genetic mutations, autoimmunity, or an idiopathic (unknown) origin. Low PTH levels result in reduced calcium levels, or hypocalcemia, leading to hypoparathyroidism symptoms such as muscle spasms, neurological issues, and kidney damage.
While there is a more robust body of evidence from studies in patients who develop hypoparathyroidism as adults, how common renal complications are in childhood-onset patients with nonsurgical hypoparathyroidism remains unclear, the team said. To learn more, the researchers analyzed electronic medical data from 143 people with this form of the disease.
Kidney calcifications
Participants had an average age of 9.5 at disease onset and 15 at hypoparathyroidism diagnosis. Most (76.9%) had idiopathic hypoparathyroidism. At study start, patients had low levels of PTH, blood calcium, and vitamin D, which helps the body absorb calcium.
Kidney calcifications, or calcium deposits, were present in 24.6% of the participants, detected at an average age of 27 after a disease duration of 18.7 years. Patients with kidney calcifications had idiopathic disease less often (58.6% vs. 82.4%).
Relative to participants without renal calcifications, those with these deposits were more likely to have elevated urinary calcium (52.7% vs. 35.6%) and kidney insufficiency (17.2% vs. 3.7%). They were also treated with a significantly higher dose of hydrochlorothiazide (42.2 mg/day vs. 25 mg/day), and tended to be younger at disease onset (8 vs. 11). Hydrochlorothiazide is a diuretic, used to stimulate urine production.
After adjusting for the disease cause, the blood calcium-phosphate product was an independent risk factor for kidney calcification, with a cutoff value of approximately 42 mg²/ dL².
“Related prospective studies are needed to further clarify whether controlling the [calcium-phosphate product] level to lower than 42 mg²/dL² will increase the risk of symptomatic hypocalcemia and hypocalcemia-related hospitalizations in the future,” the team wrote. “Clinicians should make a tradeoff to balance the risk of hypocalcemia and the level of [calcium-phosphate product].”
During follow-up, nine patients (6.3%) developed kidney insufficiency, as indicated by a significantly lower estimated glomerular filtration rate (a measure of how well the kidneys filter blood) at the last visit. Patients’ average age at kidney insufficiency diagnosis was 23, and they had an average disease duration of 22.4 years.
Those with kidney insufficiency were younger at disease onset (5.1 vs. 10.6) and more commonly had kidney calcifications (55.6% vs. 22.4%). They also had a different distribution of hypoparathyroidism causes.
Certain hypoparathyroidism types, kidney calcifications, and the highest blood calcium level were risk factors for kidney insufficiency.
“To reduce [kidney calcification] risk in childhood-onset [nonsurgical hypoparathyroidism] patients on conventional treatment, it is essential to consistently control the [blood calcium-phosphate product],” the researchers wrote. “Hypercalcemia [high calcium] during the treatment should be avoided to prevent [kidney insufficiency].”
