Calcium is an element that plays an important role in various functions of the body. Calcium contributes to the strength of bones and teeth while also playing a role in muscle contractions and regulating a normal heart rhythm. Studies have shown that most of the calcium is stored in teeth and bones while the remaining calcium circulates through the bloodstream, with its levels regulated via the parathyroid gland, the hormone calcitonin, and the absorption of vitamin D. When calcium levels are not in balance, it can have severe repercussions on biological processes and one’s health.
Calcium-Regulating Hormones
Calcium levels in the body are regulated by parathyroid hormones. These hormones are secreted from the parathyroid gland, which is situated behind the thyroid gland as a small rice grain-like gland. The parathyroid hormones regulate the rate at which calcium should be released from the bones into the bloodstream and determine calcium reabsorption via the kidneys. Another hormone that helps to regulate calcium levels in the body is calcitonin. This hormone is secreted from the thyroid gland and regulates calcium levels via two pathways.
The first method is by inhibiting the work of osteoclasts in bones. Osteoclasts are cells that break down bone to form new bone. When osteoclasts break down bone, calcium is released into the bloodstream; thus, calcitonin reduces the amount of calcium in the bloodstream by inhibiting this process.
The second method that calcitonin uses is to decrease the reabsorption of calcium from the kidneys into the bloodstream, also causing a decrease in calcium levels in the body. Vitamin D is another crucial factor for calcium absorption. In cases of insufficient vitamin D, dietary calcium’s absorption rate drops by about a quarter compared to when there is sufficient vitamin D. Vitamin D ensures optimal calcium absorption, helping to maintain normal calcium levels and ensuring the body functions properly.
Hypercalcaemia
Causes
Hypercalcaemia refers to an increased rate at which calcium is absorbed or released, resulting in higher-than-normal levels of calcium in the body. This condition is most often caused by hyperparathyroidism, which is when the parathyroid is overactive. Primary hyperparathyroidism occurs when the parathyroid produces excessive amounts of parathyroid hormones, creating an increase in calcium levels in the body, which can have serious health repercussions.
Secondary hyperparathyroidism is due to another condition that initially caused lower calcium levels, leading the parathyroid to enlarge as it tries to compensate. This often occurs due to kidney-related problems. Various cancers and medications, such as excessive vitamin D intake and thiazide diuretics, can also cause hypercalcaemia.
Signs and Symptoms
Hypercalcaemia usually affects females aged 50 years and older, especially post-menopause. Patients typically present with symptoms such as muscle weakness, constipation, abdominal pain, frequent urination, and increased thirst.
Diagnosis and Treatment
Hypercalcaemia is usually diagnosed via a blood test that measures calcium levels. To confirm the diagnosis, a parathyroid hormone blood test and a vitamin D blood test may also be requested, along with imaging scans of the parathyroid gland. In severe cases where hyperparathyroidism is the cause, surgery may be considered to remove the overactive glands. In milder cases, patients may be advised to drink more water, stop taking calcium supplements, and consult their doctor to switch from thiazide diuretics to a non-thiazide alternative.
Hypocalcaemia
Causes
Hypocalcaemia is defined by lower-than-normal levels of calcium in the body. Although this condition is less common than hypercalcaemia, it can be life-threatening if left untreated. Hypocalcaemia is most often caused by hypoparathyroidism, where the parathyroid glands do not produce enough parathyroid hormones, leading to insufficient calcium production and release from bones into the bloodstream. Another common cause is abnormally low levels of vitamin D, which impairs calcium absorption.
Kidney failure can also be a primary factor. Certain medications, such as bisphosphonates used to increase bone density, can also cause hypocalcaemia. Low magnesium levels indirectly cause low calcium levels, as the parathyroid gland requires magnesium to produce parathyroid hormone. In some cases, a genetic disorder can cause hypocalcaemia, particularly in infants. Hypocalcaemia can affect individuals of any age, from infancy to old age.
Signs and Symptoms
Hypocalcaemia can present with various life-threatening symptoms, such as severe muscle cramps, abnormal heart rhythms, seizures, and laryngospasm, which causes difficulty breathing.
Diagnosis and Treatment
Hypocalcaemia is diagnosed through blood tests that analyse calcium, parathyroid hormone, magnesium, and vitamin D levels. In some cases, a bone imaging test or an ECG may be required to check heart rhythms. Treatment typically involves calcium and vitamin D supplements, along with dietary adjustments to improve calcium levels. If the parathyroid gland is the cause, a synthetic hormone may be administered. In severe cases, intravenous calcium gluconate can be given to restore calcium balance.
