Calcium in urine (daily urine)
Why this test?
- To determine the amount of calcium consumed and its absorption in the intestines.
- To find the causes of calcium loss from the bones (osteoporosis).
- For the diagnosis of kidney diseases.
- To evaluate the functions of the parathyroid glands.
In what cases is it prescribed?
- Calcium in urine, unlike all other indicators of urine composition, is rarely investigated.
- When diagnosing diseases of the parathyroid glands and familial hypocalciuric hypercalcemia (insufficient excretion of calcium in the urine due to a violation of the intrarenal mechanism).
- With symptoms of urolithiasis: sharp and sharp pain in the right or left lumbar region, the spread of this pain below and several to the side areas of the abdomen, urination disorders, as well as the appearance of blood in the urine (this symptom alone is enough).
- In the diagnosis of digestive disorders, which may concern the small intestine, where the absorption of the main nutrients takes place (in complex with other tests).
Every day we lose some calcium after it is filtered by the kidneys and excreted in the urine. This analysis allows you to determine the daily loss of calcium through the kidneys. Calcium is a cation that is absorbed into the general bloodstream from food. It participates in bone formation, nerve impulse transmission, muscle contraction, and blood clotting. Calcium is in the bones, circulates in the blood, is filtered by the kidneys and is mostly absorbed back - at a normal level in the blood. When the concentration of serum calcium increases, the kidneys slow down the reverse reabsorption processes, due to which the level of calcium in the urine increases.
The balance of excretion and absorption of calcium is closely related to phosphate (phosphates are salts of phosphoric acid). When the concentration of calcium in the blood increases, the level of phosphate decreases, when the content of phosphate increases, the proportion of calcium decreases. Mechanisms of phosphorus-calcium exchange: -parathyroid glands with a high phosphate content (at a low calcium level) secrete parathyroid hormone, which stimulates osteoclasts, which destroy bone tissue, thereby increasing the concentration of calcium in the blood; - with a high level of calcium in the blood, the thyroid gland secretes calcitonin, which causes calcium to move from the blood to the bones; - parathyroid glands also activate vitamin D, increasing the absorption of calcium in the gastrointestinal tract and the reabsorption of the cation in the kidneys. A urine calcium test is needed to assess calcium intake and/or the balance between calcium absorption, bone resorption, and renal calcium excretion.