Parathyroid Hormone function
Parathyroid hormone (PTH) is a hormone that regulates the level of calcium in the blood, not in bones. Calcium is one of the most important and common minerals in the body. It helps in nerves work, muscles contract, blood clots, and heart function properly.
PTH is produced by four small glands called parathyroid glands, which are present behind the thyroid gland in the neck. Sometimes, these glands can become enlarged or develop tumours, affecting the amount of PTH they secrete.
PTH affects the level of calcium in the blood by acting on three main organs: the kidneys, the intestines, and the bones. When Parathyroid Hormone levels are low, it causes the kidneys to reabsorb more calcium from the urine and excrete more phosphate (a mineral that helps balance calcium). This lowers the amount of calcium in the blood (hypocalcemia) and raises the amount of phosphate in the blood (hyperphosphatemia). When PTH levels are high, it causes the kidneys to excrete more calcium into the urine and reabsorb less phosphate from the urine. This raises the amount of calcium in your blood (hypercalcemia) and lowers the amount of phosphate in the blood (hypophosphatemia).
PTH action:
PTH also affects the level of vitamin D in the body. Vitamin D is a hormone that helps increase the absorption of calcium from food and prevents its loss from the body. Vitamin D is mainly produced by the skin when exposed to sunlight. Parathyroid Hormone stimulates vitamin D production by increasing its activity in certain cells.
PTH also affects bone health by influencing bone remodelling, which is an ongoing process where bone tissue is alternately resorbed (broken down) and rebuilt over time. PTH stimulates bone resorption by activating osteoclasts (cells that break down bone) and inhibiting osteoblasts (cells that build up bone). This increases bone turnover and releases more calcium into the bloodstream.
Factors affecting PTH levels, such as diet, medications, diseases, ageing, stress, exercise, and hormones. Abnormal levels of PTH can cause various symptoms related to high or low calcium levels in the blood or bones. Some examples are:
- High PTH: nausea, vomiting, constipation, weakness, fatigue, muscle cramps, irregular heartbeat, confusion, depression, kidney stones, kidney damage, bone pain, fractures
- Low PTH: tingling sensations, muscle aches, fatigue, low calcium levels, high phosphate levels, kidney stones, kidney damage
Diagnosis of abnormal Parathyroid Hormone (PTH) levels
The diagnosis of abnormal PTH levels involves measuring them in a blood sample using a test called serum parathyroid hormone assay or 25-hydroxyvitamin D assay. The treatment depends on the cause and severity of abnormal PTH levels. Some possible treatments are:
Treatment of PTH abnormalities
- Medications: These include bisphosphonates (drugs that slow down bone resorption), calcimimetics (drugs that mimic calcium binding to parathyroid hormone receptors), vitamin D analogues (drugs that increase vitamin D production), antacids (drugs that neutralize stomach acid), phosphate binders (drugs that prevent phosphate absorption), antibiotics (drugs that treat infections), diuretics (drugs that increase urine output), anticonvulsants (drugs that prevent seizures), antidepressants (drugs that treat depression), etc.
- Surgery: This involves removing part or all of one or more parathyroid glands if they are enlarged or have tumours.
- Replacement therapy: This involves taking synthetic forms of vitamin D or calcium supplements if they are deficient due to malabsorption or other causes
