parathyroid hormone

(noun)

A hormone produced by the parathyroid gland that acts to increase blood calcium levels by stimulating osteoclasts to release calcium from the bone.

Related Terms

  • parathyroid gland
  • calcitonin
  • calcium
  • vitamin D

(noun)

A polypeptide hormone that is released by the chief cells of the parathyroid glands and is involved in raising the levels of calcium ions in the blood.

Related Terms

  • parathyroid gland
  • calcitonin
  • calcium
  • vitamin D

Examples of parathyroid hormone in the following topics:

  • Parathyroid Hormone

    • Parathyroid hormone maintains the body's calcium levels by increasing the absorption of calcium from the bones, kidneys, and GI tract.
    • When blood calcium levels drop below a certain point, the calcium-sensing receptors in the parathyroid gland are activated, and the parathyroid glands release parathyroid hormone (PTH) into the blood.
    • Parathyroid hormone acts to increase blood calcium levels, while calcitonin acts to decrease blood calcium levels.
    • This interaction between parathyroid hormone and calcitonin is also an important part of bone remodeling.
    • Parathyroid hormone regulates the levels of calcium in the blood. to the parathyroid glands.
  • Overview of the Parathyroid Glands

    • The parathyroid glands are small endocrine glands in the neck that produce parathyroid hormone.
    • The parathyroid glands are small endocrine glands—approximately the size of a grain of rice—in the neck that produce parathyroid hormone.
    • The two parathyroid glands on each side that are positioned higher are called the superior parathyroid glands, while the lower two are called the inferior parathyroid glands.
    • When blood calcium levels drop below a certain point, calcium-sensing receptors in the parathyroid gland are activated to release parathyroid hormone (PTH) into the blood.
    • The parathyroid gland in relation to the thyroid gland.
  • Calcium and Phosphate Balance Regulation

    • Absorption is controlled by vitamin D while excretion is controlled by parathyroid hormones.
    • However, the distribution from bone to plasma is controlled by both the parathyroid hormones and vitamin D.
    • It is the ionized calcium concentration that is monitored by the parathyroid gland and if low, parathyroid hormone secretion is increased.
    • Any excess is excreted by the kidney and this excretion is increased by the parathyroid hormone.
    • Plasma phosphate has no direct effect on parathyroid hormone secretion; however, if it is elevated it combines with Ca++, decreasing ionized Ca++ in plasma, and thereby increasing parathyroid hormone secretion.
  • Parathyroid Gland Disorders

    • The single major disease of parathyroid glands is over activity of one or more of the parathyroid lobes, which make too much parathyroid hormone, causing a potentially serious calcium imbalance.
    • The use of ultrasound-guided FNA, and parathyroid hormone washings can confirm the abnormal glands.
    • In secondary HPT, the parathyroid glands make too much parathyroid hormone (PTH) because the kidneys have failed, and the calcium and phosphorus are out of balance.
    • Hypoparathyroidism is decreased function of the parathyroid glands with under production of parathyroid hormone.
    • Pseudohypoparathyroidism is a condition associated primarily with resistance to the parathyroid hormone.
  • Bone and Calcium Homeostasis

    • Calcium release from bone is regulated by parathyroid hormone.
    • It circulates as a hormone in the blood, regulating the concentration of calcium and phosphate in the bloodstream and promoting the healthy growth and remodeling of bone.
    • At the same time, the parathyroid glands reduce parathyroid hormone secretion into the blood.
  • Action of Thyroid Hormones

    • The primary function of the thyroid is to produce the hormones triiodothyronine (T3), thyroxine (T4), and calcitonin.
    • T4 is thought to be a pro-hormone to the more metabolically active T3.
    • Calcitonin is another hormone released by the thyroid gland that is responsible for modulating blood calcium levels in conjunction with parathyroid hormone, which is released from the parathyroid.
    • Only a very small fraction of the circulating hormone is free—T4 0.03% and T3 0.3%.
    • Only the free fraction has hormonal activity.
  • Bone Tissue and the Effects of Aging

    • Calcium-sensing membrane receptors in the parathyroid gland monitor calcium levels in the extracellular fluid.
    • Low levels of calcium stimulates the release of parathyroid hormone (PTH) from chief cells of the parathyroid gland.
    • High levels of calcium in the blood, on the other hand, lead to decreased PTH release from the parathyroid gland.
    • In addition, certain medical conditions such as hormone imbalances can cause bone resorption to increase, leading to increased susceptibility to fractures.
  • Overview of Endocrine Glands

    • A collection of endocrine glands makes up the endocrine system: the pituitary (anterior and posterior lobes), thyroid, parathyroid, adrenal (cortex and medulla), pancreas and gonads.
    • Two hormones—oxytocin and antidiuretic hormone (ADH)—are produced and released this way.
    • There are four parathyroid glands, all located on the thyroid gland.
    • All four glands also secrete parathyroid hormone, or PTH, which causes calcium to be released from the bones back into the extracellular fluid.
    • Differentiate among the types of endocrine glands (pituitary [posterior pituitary, anterior pituitary], thyroid, parathyroid, adrenal, and pancreas) in the endocrine system
  • Interactions of Hormones at Target Cells

    • Hormones that act to return body conditions to within acceptable limits from opposite extremes are called antagonistic hormones.
    • It can be used to describe situations in which the presence of one hormone, at a certain concentration, is required to allow a second hormone to fully affect the target cell.
    • When conditions return to normal, hormone production is discontinued.
    • Hormones that act to return body conditions to within acceptable limits from opposite extremes are called antagonistic hormones.
    • The two glands most responsible for homeostasis are the thyroid and the parathyroid.
  • Development of the Endocrine System

    • Increases in hormone activity decrease the production of that hormone.
    • The immune system and other factors contribute to maintaining constant levels of hormones.
    • The main endocrine glands are the hypothalamus (neuro-endocrine gland), pituitary (anterior and posterior lobes), thyroid, parathyroid, adrenal (cortex and medulla), pancreas, and gonads.
    • These hormones increase the metabolic activity of the body's cells.
    • This hormone, produced by the pituitary gland, is known as thyroid-stimulating hormone (TSH).
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