Parathyroid and Adrenal Flashcards
normal levels of calcium in blood
9-10 mg/dl
Calcium distribution
40% combined with plasma proteins
10% bound to low-molecular weight substances (citrate or phosphate)
50% ionized
Chief cells
Most numerous paranchymal cells of the parathyroid. They secrete PTH
Oxyphil cells
These are a minor cell type in parathyroid glands.
They are not secretory and increase in number with age
What is the relationship of Vitamin D and Calcium?
Vitamin D is important for the absorption of calcium from the intestinal tract
This results when there is a decline in plasma calcium levels
Hypocalcemia
Lethal if calcium levels fall below
4 mg/dl
Hypercalcemia: when levels are approximately 12 mg/dl
Causes depression of nervous system, constipation and lack of appetite
When levels are as high as 17 mg/dl, what happens to calcium phosphate crystals
Calcium phosphate crystals precipitate throughout the body
Calcitonin
lowers serum calcium
Function of PTH
Regulates calcium and phosphate levels in the blood:
Causes release of calcium and phosphate from the calcified bone matrix (bone resorption).
Reduces excretion of calcium by the kidneys.
Increases phosphate excretion by the kidneys.
Increases absorption of calcium from the intestine.
These effects cause blood calcium levels to increase but blood phosphate levels to decrease
Hypoparathyroidism
This condition leads to inactivation of osteoclasts: calcium reabsorption is decreased leading to hypocalcemia
Treatment for hypoparathyroidism
Vitamin D and its analogs
Hyperparathyroidism
Usually due to a tumor of the parathyroid glands. Causes extreme osteoclastic activity in bones. In severe cases, bone may be entirely eaten away.
Mild parathyroidism can cause formation of
Kidney stones
Regulated by a simple feedback system. When calcium levels are low
PTH is secreted
Treatment
Cinacalcet:
calcimimetic drug= reduces PTH secretion by influencing the parathyroid calcium sensing receptors
Treatment of osteoporosis
Adequate intake of calcium and vitamin D
Bisphosphonates: alendronate, risedronate, ibandronate, zoledronic acid
PTH fragment: anabolic (bone building) compound when used intermittently
calcitonin: Inhibits osteoclasts and increases bone mass
Estrogen/Hormone Therapy (ET/HT)
total loss of aldosterone
leads to death within 3 days to 2 weeks
Hyperadrenalism (Cushing’s disease)
Caused by cortisol secreting tumor or hyperplasia of adrenal cortex due to increased secretion of ACTH
