The human body relies on chemical messengers to maintain balance and proper function. Parathyroid hormone (PTH) is a key regulator that influences various bodily processes, underscoring its importance for overall well-being.
What is Parathyroid Hormone?
Parathyroid hormone (PTH) is a peptide hormone produced and released by the parathyroid glands. These are typically four small glands located in the neck, usually behind the thyroid gland. Once secreted, PTH circulates throughout the bloodstream, acting as a chemical signal to various organs. Its primary role involves maintaining stable levels of certain minerals within the blood.
Its Role in Calcium and Phosphate Balance
The main function of parathyroid hormone is to regulate the levels of calcium and phosphate in the blood. When blood calcium levels drop, the parathyroid glands release PTH. This hormone then acts on three primary targets: bones, kidneys, and the small intestine, to restore mineral balance.
In the bones, PTH stimulates the release of calcium from mineral reserves stored within bone tissue. It does this by indirectly promoting the activity of osteoclasts, cells responsible for bone resorption. PTH also inhibits osteoblast activity, which are the cells that form new bone, contributing to increased calcium levels in the blood.
In the kidneys, PTH reduces the amount of calcium lost in urine by enhancing its reabsorption. Conversely, it increases the excretion of phosphate in the urine. PTH also stimulates the kidneys to convert inactive vitamin D into its active form, calcitriol. This activated vitamin D then indirectly enhances calcium absorption from food in the small intestine.
Conditions Caused by Imbalance
Disruptions in parathyroid hormone production can lead to health issues due to imbalances in calcium and phosphate levels.
Hyperparathyroidism
Hyperparathyroidism occurs when the parathyroid glands produce too much PTH, leading to elevated calcium levels in the blood (hypercalcemia). This overproduction is often caused by a benign growth, called an adenoma, on one or more of the parathyroid glands. Symptoms can include fatigue, bone and joint pain, muscle weakness, increased thirst, frequent urination, and in more severe cases, kidney stones or bone weakening (osteoporosis).
Hypoparathyroidism
Conversely, hypoparathyroidism results from insufficient PTH production, leading to low calcium and elevated phosphate levels in the blood. The most common cause is accidental damage to the parathyroid glands during neck or thyroid surgery. Symptoms include tingling or burning sensations in the fingers, toes, and lips, muscle cramps or spasms (tetany), headaches, and fatigue.
Diagnosis and Treatment Approaches
Diagnosing parathyroid hormone disorders involves blood tests to measure levels of calcium, parathyroid hormone, and vitamin D. A high calcium level with an elevated or normal-range PTH level can indicate hyperparathyroidism. For hypoparathyroidism, diagnosis shows low calcium and low PTH levels, often alongside high phosphate.
Hyperparathyroidism Treatment
Treatment often focuses on addressing the overactive gland. For primary hyperparathyroidism, surgical removal of the affected gland or glands (parathyroidectomy) is a common and often curative approach. In cases where surgery is not suitable, medications may be used to manage calcium levels or address underlying causes, such as vitamin D deficiency or kidney disease.
Hypoparathyroidism Treatment
Treatment primarily involves lifelong supplementation with calcium and activated vitamin D to restore normal blood calcium levels. The goal of these treatments is to alleviate symptoms and prevent long-term complications by maintaining appropriate calcium and phosphate balance in the body.