Parathyroid hormone (PTH)

Definition

Parathyroid hormone (PTH) is a hormone produced by the parathyroid glands that regulates calcium and phosphate levels in the blood. It plays a critical role in bone metabolism and calcium homeostasis.

5 Must Know Facts For Your Next Test

1. PTH increases blood calcium levels by stimulating osteoclast activity, increasing intestinal absorption of calcium, and promoting renal reabsorption of calcium.
2. A deficiency or excess of PTH can lead to disorders such as hypoparathyroidism or hyperparathyroidism.
3. PTH secretion is regulated by the serum calcium level via a negative feedback loop.
4. Calcitriol (active vitamin D) works synergistically with PTH to enhance calcium absorption from the gut.
5. Pharmacological agents that mimic or inhibit PTH are used in the treatment of osteoporosis and other metabolic bone diseases.

Review Questions

• What primary functions does parathyroid hormone (PTH) perform in the body?
• How does PTH regulate serum calcium levels?
• Name one disorder associated with an imbalance of PTH.

Related terms

Calcitonin: A hormone produced by the thyroid gland that lowers blood calcium levels.

Osteoclasts: Cells that break down bone tissue, a process stimulated by PTH to release calcium into the blood.

Hypoparathyroidism: A condition characterized by insufficient secretion of parathyroid hormone, leading to low levels of blood calcium.