Endocrinology Flashcards
(16 cards)
3 routes of hormonal secretion
Saliva, urine and feces
What must happen in order for a circulating hormone that is bound to a protein to become active?
It must unattach from the protein because it is activated.
Definition of a hormone
A hormone is a chemical released by a cell, gland, or an organ that affects cells in other parts of the organism.
Parathyroid hormone (PTH)
PTH is released as a polypeptide and acts to increase the concentration of calcium in the blood by releasing it from the large reservior contained in the bones.
Calcitonin (CT)
CT is also secreted as a polypeptide by C cells that lay within the thyroid cells and release directly into the bloodstream. Works to oppose the effects of PTH, therefore reducing the amount of Ca in the blood.
What is the main stimulus for secretion of PTH?
Low Ca levels OR high phosphate levels.
What are the 4 key actions of PTH discussed in lecture?
- transfers Ca from bone to blood
- remodeling of bone
- decreases reabsorption of phosphate
- activates Vit D therefore increasing absorption of dietary Ca
What are the 3 key actions of CT discussed in lecture?
- its goes against PTH
- blocks renal reabsorption of Ca
- inhibits GIT reabsorption of Ca by inhibiting activation of Vit D.
What has to happen to Vit D before it can be used?
Vit D is considered to be devoid of direct biological activity. It must first be hydroxylated in the liver and then in the kidney. It then plays a key role in enhancing intestinal absorption of Ca and phosphate.
Definition of hypocalcemia
Refers to low blood calcium concentrations. Clinical signs of this disorder reflect increased neuromuscular excitability and include muscle spasms, tetany and cardiac dysfunction.
Definition of hypercalcemia
Hypercalcemia indicates a concentration of blood calcium higher than normal. Elevations can lead to diffuse precipitation of calcium phosphate in tissues, leading to widespread organ dysfunction and damage.
What are three organs that work very closely to supply calcium to blood AND removing it from the blood when necessary.
- Small intestines
- Bone
- Kidney
Maintaining normal blood calcium and phosphorus concentrations is managed through what three hormones?
- PTH
- Vit D
- Calcitonin
Where does the PTH come from and where are its receptors in the body?
PTH comes from the parathyroid glands which are around the neck/under the jaw. PTH acts upon the PTH 1 receptor which are in high levels in bones and kidneys. PTH2 receptors are located in the CNS, pancreas, testis, and placenta.
Where does Calcitonin come from and where are its receptors in the body?
CT comes from c-cells that are located in the thyroid which is in the neck/under the jaw. The CT receptor is found on osteoclasts, in the kidney and in regions of the brain.
Where does VIt D come from and where are its receptors in the body?
Vit D can be ingested from the diet or synthesized in the skin from cholesterol when sun exposure is adequate. it is converted to calcitriol which is the biologically active form of Vit D. It circulates in the bloodstream.
