Parathyroid Disorders Flashcards
PTH acts on
Bone, kidneys, and intestines to increase blood calcium levels
The absence of parathyroid glands is
Incompatible with life
The parathyroid gland has two types of cells
Chief cells and oxyphil cells
What is the main function of chief cells?
Manufacturing, storing and rapidly releasing PTH in response to alterations of blood calcium levels
Chief cells stain slightly
Eosinophilic
Chief cells contain secretory granules that contain
PTH
Which cells are inactive chief cells?
Oxyphil cells
Oxyphil cells may take on a water-clear apperance due to the presence of
Cytoplasmic glycogen
Oxyphil cells tend to be slightly larger than chief cells, have acidophilic cytoplasm and are tightly packed with
Mitochondria
Oxyphil cells have secretory granules that are slightly sparse or
Absent
As people get older, what increases in the parathyroid gland?
Adipose tissue and oxyphil cells
Wht are the normal serum calcium levels?
8.5 to 10.5
What effect does PTH have on bone?
Inhibits osteoblast activity and stimulates osteoclast activity aka increases bone resorption
What effect does PTH have on the kidneys?
PTH increases calcium reabsorption within the distal convoluted tubules and blocks phosphate reabsorption in the proximal tubules
PTH stimulates the production of what vitamin?
D within the proximal tubules
What effect does PTH have on the GI system?
Increased calcium reabsorption
What is primary hyperparathyroidism?
Autonomous overproduction of PTH. Usually secondary to adenoma or hyperplasia of parathyroid tissue
What is secondary hyperparathyroidism?
Hypocalcemia triggers a compensatory increased secretion of PTH (example: kidney disease)
What is tertiary hyperparathyroidism?
Consequence of prolonged hypocalcemia even after it is corrected. Even we we correct the hypocalcemia, PTH doesnt go down when it is supposed to.
Hyperparathyroidism is an important cause of?
Hypercalcemia
Primary hyperparathyroidism is a common endocrine disorder secondary to
Adenomas 85 to 95%
Primary hyperplasia (diffuse or nodular) 5-10%
Parathyroid carcinoma
What is the most common cause of primary hyperparathyroidism?
Pararhyroid adenoma
MEN-1 mutations are associated with?
Parathyroid adenoma
Overexpression of cyclin D1 secondary to cyclin D1 gene inversions are associated with
Parathyroid adenomas
What are the symptoms of primary hyperparathyroidism?
Painful bones, renal stones, abdominal groans, and psychic moans
What are other clinical symptoms of primary parathyroidism?
Bone pain secondary to fractures, constipation, nausea, peptic ulcers, pancreatitis, gallstones, depression, lethargy, eventually seizures, myalgias, weakness, fatigue, aortic or mitral valve calcifications
parathyroid adenomas are almost always
Solitary
-may be present at an ectopic site (mediastinum)
Parathyroid adenomas are mostly composed of
Polygonal chief cells with small centrally placed nuclei
the growth of parathyroid carcinoma is limited to
1 gland
What is the only criteria for parathyroid carcinoma?
Invasion of surrounding tissues and metastasis
In parathyroid carcinoma we can appreciate
Bands of fibrous tissue between the nests of carcinoma cells
What is the leading cause of secondary hyperparathyroidism?
Renal failure
What are some other secondary causes of secondary hyperparathyroidism?
Deficient dietary calcium, steatorrhea, vitamin D deficiency
Decreased phosphate excretion is also associated with
Secondary hyperparathyroidism
What is the main cause of acquired hypoparathyroidism?
Surgically acquired
Autoimmune hypoparathyroidism is associated with
Autoimmune polyendocrine syndrome type 1 along with chronic mucocutaneous candidiasis and primary adrenal insufficiency
Autosomal dominant hypoparathyroidism is due to
Gain of function mutations in the calcium sensing receptor gene (CASR)
Heighened calcium sensing suppresses what?
PTH which result in hypocalcemia and hypercalciuria
Familial isolated hypoparathyroidism (the autosomal dominant version) is associated with
A mutation in the gene encoding PTH precursor peptide
The autosomal recessive verison of FIH is associated with?
A loss of function mutation in the transcription factor gene glial cells missing-2 (GCM2)
What is the deletion in Di George syndrome?
22q11.2 deletion
Di George syndrome leads to
Congenital malformations of the heart, parathyroid and thymus
What is the main manifestation of hypocalcemia?
Tetany
Tetany is characterized by
Neuromuscular irritability
What other symptoms can be seen in hypoparathyroidism?
Perioral numbness
Paraesthesias of the distal extremities and carpopedal spasm
Life-threatening laryngospasm
Generalized seizures
What are some classic findings on hypoparathyroidism?
Chvostek sign- tapping along the facial nerve induces contractions of the muscles of the eye, mouth or nose
Trousseau sign- carpal spasms produced by occlusion of the circulation to the forearm and hand with a blood pressure cuff for several minutes
Hypoparathyroidism can induce
Mental status changes
Hypoparathyroidi can induce intracranial manifestations like
Calcifications of the basal ganglia, parkinsonian-like movement disorders, increased ICP with resultant papilledema
Hypoparathyroidism can result in
Calcification of the lens and cataract formation
What cardiovascular problems can someone with hypoparathyroidism have?
Prolongation of the QT interval
What dental abnormalities can be seen in hypoparathyroidism?
Dental hypoplasia, failure of eruption, defective enamel and root formation, abraded carious teeth
