Parathyroid Pathophysiology Flashcards
how many parathyroid glands are there?
4
PTH
- parathyroid hormone, parathormone
- released into the bloodstream by negative feedback mechanism
- depended on plasma calcium concentration
- half-life is 4 min
avg PTH level
8-51 pg/mL
hypocalcemia
release parathormone
hypercalcemia
suppress synthesis and release of parathormone
function of PTH
maintains normal plasma calcium concentration
what three interfaces does calcium move across
- GI tract
- renal tubules
- bone
resorption
- in context of physiology is absorption into the circulation
- osteoclasts break down the bone tissue and release minerals, resulting in transfer of calcium from bone tissue to the blood
osteoclasts
- found on surface of bones and are multi-nucleated cells that contain numerous mitochondria and lysosomes
- break down bone tissue by digestion and degradation
calcitonin
- opposes effects of PTH
- secreted by parafollicular cells in thyroid
- secretion stimulated by hypercalcemia
PTH three ways of raising blood calcium
- bone resorption by osteoclasts
- increased calcium reabsorption by kidneys (and decreased phosphate reabsorption)
- increased calcium reabsoprtion by intestines
3 ways calcitonin lowers blood calcium
- inhibits osteoclast activity in bones
- inhibits renal tubular cell reabsorption of Ca2+
- inhibits Ca2+ absorption in the intestines
vitamin D
- fat soluble
- increases intestinal absorption of calcium, mag, and phos
- contributes to calcium homestasis and metabolism
- vitamin D receptors located in the intestines, kidneys, bone, and parathyroid gland
vitamin D receptors functions
- helps transport proteins absorb calcium in intestine
- bone resorption
- reabsorption of calcium in distal nephron
normal total calcium level
- includes bound and free
- 9.5-10.5 mg/dL
normal iCal
4.75-5.7 mg/dL
free calcium
calcium in the body
- 50% bound to albumin
- 40% ionized
- 10% bound to chelating agents
acidosis and serum calcium
increases serum calcium
protein binding decreases as pH decreases
increased ionized fraction
alkalosis and serum calcium
decreases serum calcium
decreased ionized fraction
how much does calcium increase with each 0.1 decrease in pH?
0.05 mmol/L
biological functions of calcium
- bone formation
- reservoir for ECF
- blood clotting
- excitability of nerve and muscle
- metabolic regulation for action of hormones and enzyme activation
disorders r/t PTH
- reduced production of PTH - DiGeorge, CATCH 22, autoimmune
- impaired PTH due to peripheral resistance
- parathyroid gland adenomas
hyperparathyroidism
- excess production of PTH
- most common cause of hypercalcemia defined as total serum calcium above 10.4
- classifications = primary, secondary, ectopic
primary hyperparathyroidism causes
- benign adenoma (80-90%)
- hyperplasia
- carcinoma
s/s hyperparathyroid
- involve kidneys and skeletal system
- calcium deposits in renal parenchyma or recurrent nephrolithiasis
- skeletal pathology
- symptoms more common at calcium levels above 11.5-12
diagnosis of hyperparathyroid
- PTH assay
- calcium level
- vitamin D levels
- renal function
- CT scan
- has anything happened to neck?
- albumin?
medical management of hyperparathyroid
- used for mild, asymptomatic disease
- mild hypercalcemia (12) –> hydration
- moderate to severe hypercalcemia (13-15) –> IV saline hydration and furosemide to promote Na/Ca diuresis
surgical management of hyperparathyroid
- definitive treatment
- intraop PTH assay measured before and at 5 min intervals after adenoma removal to confirm a rapid fall to normal
multiple gland hyperplasia treatment
- three removed with partial excision of fourth (leaving a good blood supply)
- total parathyroidectomy performed with immediate transplantation of a removed, minced parathyroid gland into the forearm muscles
hypoparathyroidsim
- absence or deficiency of PTH secretion
- resistance of peripheral tissue to effects of hormone
- iatrogenic (removed surgically with thyroidectomy)
- result = hypocalcemia
hypocalcemia s/s
- neuronal irritability
- skeletal muscle spasms
- tetany (reduced calcium lowers threshold for depolarization)
- seizures
- fatigue and mental status changes
- prolonged AT
- CHF (chronic)
- hypotension (acute)
- chvostek’s sign
- trousseau’s sign
what can acute hypocalcemia present with?
- stridor
- laryngospasm
- apnea
hypocalcemia treatment
- electrolyte replacement
- calcium and vitamin D
- hypomagnesemia managed with oral or IV replacement
- severe requires 10-20 mL of 10% calcium gluconate OR 3-5 mL of 10% calcium chloride followed by a continuous infusion of calcium (1-2 mg/kg/h)
anesthesia and hypocalcemia
-treat prior to elective surgery
major anesthetic risks of hypocalcemia
- decreased cardiac contractility
- dysrhythmias
- tetany
- altered response to muscle relaxants
- risk for laryngospasm
overactive parathyroid gland
- 1 in 100 people will develop parathyroid gland tumor
- treatment = surgical removal
- without treatment = fatigue, bad memory, kidney stones, osteoporosis
anesthetic management of parathyroidectomy
- concern for cardiac dysrhytmias secondary to elevated calcium
- NIMs ETT (assess RLN)
- effects of NMBDs unpredictable (consider qualitative NMB monitoring)
- careful positioning (risk for fractures)
- post op complications similar to thyroid
post op complications of parathyroidectomy
- RLN injury
- hematoma
- hypocalcemia
PTH sampling during surgery
- baseline PTH
- scheduled PTH samples in OR at time 0 (removal of parathyroid as alerted by surgeron) AND time 5, 10, and 15 min post parathyroid removal
