The Parathyroid Gland

The parathyroid glands have two cell populations. What are they?

1. Parathyroid (chief) cells--they produce parathroid hormone (PTH). 2. Oxyphils--their function is unknown.

What is PTH?

Parathyroid hormone. 1. aka parathormone 2. Regulates calcium concentration (causes an increase of Ca2+ in body fluids) 3. Effects--PTH mobilizes calcium from bone by affecting osteoblast (contribute to bone production) and osteoclast (break down bone tissue) activity. a. PTH stimulates osteoblasts to secrete a growth factor known as RANKL. b. Osteoclasts have no PTH receptors but have RANKL receptors. c. RANKL results in an increase in osteoclast and osteoclast activity. d. With more active osteoclasts, the rates of mineral turnover and Ca2+ release accelerate. e. As bone matrix erodes, blood Ca2+ rises. 4. PTH is regulated by negative feedback from Ca2+.

Where are the parathyroid glands located?

They are in the posterior surface of the thyroid gland. There are usually two pair. A dense capsule surrounds each gland and separates it from the cells of the thyroid gland.