Parathyroid Hormone (PTH)
Pseudohypoparathyroidism
Caused by PTH hyposecretion and tisssue resistance to PTH (PTH-dependent Hypocalcemia.
Primary hyperparathyroidism
Caused by tumor or hyperplasia.
Labs of primary hyperparathyroidism
Increased PTH, increased calcium, normal or decreased phosphorous
Secondary hyperparathyroidism labs
Increased PTH, low calcium,, high phosphorous
Secondary hyperparathyroidism
Occures when the body attempts to compensate for low calcium by putting out more PTH. Usually problem in kidneys (letting go too much calcium)
Effect on calcium
PTH increases serum calcium by increasing bone resorption of calcium into blood (this requires vitamin D). Increases renal reabsorption of calcium.
Symptom of hypercalcemia
Polyuria, polydipsia, hypertension, acid-base disorders, kidney stones, etc. Can be asymptomatic.
Hypercalcemia
can be caused by malignancy or bone disease
Idiopathic hypoparathyroidism
cause unknown, rare, thought to be hereditary.
Primary hypoparathyroidism
caused by surgical removal of parathyroid gland, surgical trauma, or radiation.
PTH-Independent Hypocalcemia
caused by vitamin D deficiency
Effect on serum phosphate
decreases blood phosphate via inhibition of renal reabsorption of phosphate
Release and Regulation
ionized calcium regulates PTH release. Magnesium and vitamin D can also slightly regulate it.
pseudohypoparathyroidism
lack of renal and tissue responsiveness to PTH. Not a decrease in PTH, Kidneys do not respond to PTH, so calcium is not reabsorbed.
Lab results of primary hypoparathyroidism
low calcium and high phosphorous
Function
metabolism of calcium and phosphorous in kidney and bone.
Multiple Endocrine Neoplasia (MEN)
new tissue growth of several endocrine glands (including parathyroid).
Calcitonin
synthesized in thyroid and regulated by calcium. It decreases serum calcium by inhibiting bone resorption of Ca and decreasing kidney reabsorption of Ca, Ph, K, and Mg.
Symptoms of hypocalcemia
tetany (muscle twitching), dry skin, and hypotension
Labs of Idiopathic hypoparathyroidism
very low calcium, very high phosphorous
