Parathormone

Definition

Parathormone, also known as parathyroid hormone (PTH), is a peptide hormone produced by the parathyroid glands that plays a critical role in regulating calcium levels in the blood and bone metabolism. This hormone is essential for maintaining the balance of calcium and phosphorus in the body, influencing processes like bone resorption, renal calcium reabsorption, and intestinal calcium absorption.

5 Must Know Facts For Your Next Test

1. Parathormone increases blood calcium levels by stimulating osteoclasts, which break down bone tissue and release calcium into the bloodstream.
2. The secretion of parathormone is regulated by the serum calcium concentration; low blood calcium levels trigger its release, while high levels inhibit it.
3. PTH promotes the reabsorption of calcium in the kidneys and enhances the activation of vitamin D, which increases intestinal absorption of calcium.
4. Chronic high levels of parathormone can lead to bone density loss, making bones more susceptible to fractures and conditions like osteoporosis.
5. Parathormone works in opposition to calcitonin, balancing the effects on calcium homeostasis within the body.

Review Questions

• How does parathormone influence calcium metabolism in the body?
  • Parathormone influences calcium metabolism primarily by increasing blood calcium levels. It stimulates osteoclasts to resorb bone, releasing stored calcium into circulation. Additionally, it promotes renal reabsorption of calcium and enhances intestinal absorption through its activation of vitamin D. Together, these actions ensure that calcium levels remain within a normal range, which is vital for many physiological processes.
• Discuss how parathormone interacts with other hormones like calcitonin in maintaining calcium balance.
  • Parathormone and calcitonin have opposing roles in maintaining calcium balance. While parathormone increases blood calcium levels by stimulating bone resorption and renal reabsorption, calcitonin works to decrease blood calcium levels by inhibiting osteoclast activity. This interplay ensures that calcium homeostasis is tightly regulated. When parathormone raises calcium levels too high, calcitonin is secreted to bring those levels back down, demonstrating a delicate balance between these two hormones.
• Evaluate the implications of hyperparathyroidism on overall health and bone density.
  • Hyperparathyroidism results from excessive production of parathormone, which can significantly impact overall health and bone density. The increased activity of osteoclasts leads to accelerated bone resorption, causing bones to weaken and become more fragile over time. This condition can lead to symptoms like kidney stones due to elevated calcium levels in the blood, along with potential cardiovascular issues. The combined effects on skeletal integrity and metabolic processes underscore the importance of regulating parathormone levels for maintaining good health.

Related terms

Calcitonin:

A hormone produced by the thyroid gland that helps lower blood calcium levels by inhibiting osteoclast activity in bones.

Osteoclasts:

Bone cells responsible for the resorption of bone tissue, which is influenced by parathormone to release calcium into the bloodstream.

Hyperparathyroidism:

A condition characterized by an overproduction of parathyroid hormone, leading to elevated blood calcium levels and various health issues.