From the Guidelines
We monitor urine calcium in hypoparathyroidism to prevent hypercalciuria and its complications, such as nephrolithiasis and nephrocalcinosis, as suggested by the relationship between daily oral phosphate doses and the risk of developing nephrocalcinosis 1. In hypoparathyroidism, patients typically receive calcium and vitamin D supplements to manage hypocalcemia. However, these treatments can lead to excessive urinary calcium excretion (hypercalciuria), which may cause kidney damage.
- The goal is to maintain 24-hour urinary calcium excretion below 300 mg/day in men, below 250 mg/day in women, or ideally below 4 mg/kg/day for both sexes.
- Regular monitoring allows for timely adjustment of calcium and vitamin D supplementation.
- If hypercalciuria develops, treatment modifications may include reducing calcium or vitamin D doses, adding a thiazide diuretic like hydrochlorothiazide, as it decreases calciuria 1, or considering alternative therapies.
- Monitoring typically involves 24-hour urine collections every 6-12 months during stable disease, and more frequently when adjusting therapy or if kidney stones develop. The use of hydrochlorothiazide, which decreases calciuria, is supported by the study 1, and potassium citrate might help prevent calcium precipitation, especially in patients with low urinary citrate levels, although it should be used with caution.
From the Research
Importance of Monitoring Urine Calcium in Hypoparathyroidism
- Urine calcium levels are monitored in hypoparathyroidism to assess the risk of nephrocalcinosis, kidney stones, and renal impairment 2, 3, 4
- Hypercalciuria, or elevated urine calcium levels, can occur in patients with hypoparathyroidism, particularly those on conventional therapy with oral calcium and active vitamin D 2, 3, 4
- Monitoring urine calcium levels helps to adjust treatment and prevent long-term complications, such as nephrocalcinosis and kidney stones 4
Relationship Between Urine Calcium and Treatment
- Conventional therapy with oral calcium and active vitamin D can increase the risk of hypercalciuria and subsequent renal complications 2, 3, 4
- PTH replacement therapy, such as recombinant human PTH(1-84), can help to normalize urine calcium levels and reduce the risk of long-term complications 5, 6
- The long-acting PTH analogue, palopegteriparatide, has been shown to normalize urine levels of calcium and improve quality of life in patients with hypoparathyroidism 6
Clinical Implications
- Regular monitoring of urine calcium levels is essential in patients with hypoparathyroidism to prevent and manage renal complications 2, 3, 4
- Treatment should be adjusted based on urine calcium levels to minimize the risk of hypercalciuria and subsequent renal complications 4
- PTH replacement therapy may be considered as an alternative to conventional therapy to normalize urine calcium levels and improve quality of life in patients with hypoparathyroidism 5, 6