Parathyroid Disorders Flashcards
Calcium in the Body
Adequate calcium levels in the body are dependent on diet
Most calcium is stored in bones and teeth
Plasma calcium:
45% free ionized form
40% bound to protein (albumin)
15% complexed with anions (citrate, phosphate)
Calcium functions
Functions:
Build and maintain strong bones and teeth
Smooth muscle contraction
Cofactor for enzymatic reactions
Regulation of clotting mechanisms
Cardiac and nerve function
Parathyroid Glands
general
What cell secrets PTH
Four pea-sized glands located posterior to the thyroid gland (superior pair and inferior pair)
Chief cells synthesize, secrete, and store parathyroid hormone (PTH)
Parathyroid hormone regulates calcium levels in the blood through calcium-sensing receptors within the chief cells
Parathyroid Disorders:
Hyperparathyroidism → hypercalcemia
Hypoparathyroidism → hypocalcemia
Parathyroid Hormone (PTH)
Functions (3)
Functions:
Increases calcium andphosphate release from the bones through osteoclast activation
Increases calcium reabsorption and phosphate excretion in the distal tubule of the kidney
Increases synthesis of 1,25-dihydroxyvitamin D, (active Vitamin D),which will increase calcium absorption from the gastrointestinal tract
Parathyroid Hormone Regulation
Secretion of PTH is stimulated by:
Decreases in serumcalcium
Low levels of 1,25-dihydroxyvitamin D (active form of Vitamin D)
Calcium has a direct relationship with Vitamin D
Hyperphosphatemia
Calcium has an inverse relationship with phosphorus
As levels of phosphorus ↑, the levels of free calcium in the blood decreases, because phosphorus binds to calcium
Hypomagnesemia
Calcium has a direct relationship with magnesium
Secretion of PTH is inhibited by:
High levels of serumcalcium
Calcitonin
general
Hormone produced by the parafollicular cells (C cells) of the thyroid gland
Secretion of calcitonin is stimulated by:
Increases in serum calcium
directly opposite of PTH
calcitonin
Functions (2)
Functions:
1. Inhibits (blocks) the activity of osteoclasts (no calcium is released from bone)
2. Decreases calcium reabsorption in the kidneys
Hyperparathyroidism
general
Condition that results from increased function of the parathyroid glands with overproduction of parathyroid hormone (PTH) → hypercalcemia
Often discovered incidentally when assessing labs
♀>♂
Incidence increases after age 50 years
Hyperparathyroidism
types
Primary (Inherent disease of the parathyroid gland)
Secondary
Tertiary
Primary Hyperparathyroidism
general and causes
elevated PTH independent of calcium levels
Most common cause
95 % of cases occur sporadically Parathyroid adenoma (benign) ~85%
Parathyroid gland hyperplasia – ~15%
Parathyroid carcinoma – < 1%
5% are familial (genetic mutations) **Multiple Endocrine Neoplasia** I and 4 syndrome
Secondary Hyperparathyroidism
general and causes
elevated PTH due to chronic hypocalcemia
Due to an underlying condition that decreases serum calcium levels (abnormal calcium metabolism)
Chronic renal failure (CRF)
Bypass surgery (reduced surface area for absorption of calcium)
Celiac disease/Crohn’s disease (malabsorption)
Severe vitamin D deficiency (low dietary intake, lack of sun exposure, or malabsorption)
Tertiary Hyperparathyroidism
general
will not be tested, just know it exists and comes from long standing secondary
Due to long-standing secondary hyperparathyroidism
Hypertrophy and autonomous functioning (unregulated) of the parathyroid glands
hyperparathyroidism
clin man
Most patients are asymptomatic or present with nonspecific symptoms
Sx:
Mnemonic: “stones,bones, abdominalgroans, thrones,and psychiatric overtones”
Bone pain
Bone demineralization (osteoporosis) → pathological fractures, cystic bone lesions
Nephrolithiasis (15% of patients)
Renal loss of calcium (calciumphosphate orcalcium oxalate stones)
Abdominal cramps and constipation
Peptic ulcers and pancreatitis
Irritability, confusion, delirium, and depression
Muscle weakness and rapid muscle fatigue
Polydipsia and polyuria
Hypercalcemia-induced nephrogenic diabetes insipidus- dont worry about this
Calciphylaxis
Deposits of calcium in the skin and muscles
hyperparathyroidism
Electrocardiogram changes
AV block, short QT interval, Osborn or J waves
hyperparathyroidism
primary hyperparathyroidism
Serum Labs
calcium, phosphorus, PTH
↑ serum calcium
Measure total serumCa2+if normalalbumin
Measure ionizedCa2+if lowalbumin
↓ or normal serum phosphorus
↑ serum PTH
hyperparathyroid
urine labs
Parathyroid cancer indications
↓ urine calcium
24-hour urine for calcium/creatinine ratio required before starting any treatments
Extreme elevations of serum calcium and PTH indicate parathyroid cancer
Hyperparathyroidism
EKG
Hypercalcemia
AV block, shortened QT interval
Osborn waves with severe hypercalcemia (>14 mg/dL)
hyperparathyroidism
Tx of Asx primary disease
Monitor for the development of symptoms
Monitor serum calcium and albumin levels, calcium excretion, kidney function
Bone density measurements (hip, spine, and forearm) every 1-2 years
Avoid calcium containing antacids and supplements
Maintain adequate Vitamin D intake
Encourage physical activity to decrease bone resorption
Bisphosphonate therapy
Encourage osteoclast destruction → decreased serum calcium levels
hyperparathyroidism
Tx of Symptomatic primary disease or presence of parathyroid carcinoma
Parathyroidectomy
Will include an ipsilateralthyroidectomy for those with parathyroid carcinoma
Hypocalcemia and transient hyperthyroidism may occur postoperatively
Hypoparathyroidism
general
Condition that results from decreased function of the parathyroid glands with underproduction of parathyroid hormone (PTH) → hypocalcemia
hypoparathyroidism
causes (5)
Inadvertent damage (radiation) or removal of thyroid and/or parathyroid glands during neck surgery
Autoimmune disease
Heavy metal toxicity (iron and copper)
Iron overload disorder? Copper overload disorder? HFE!
Hemochromatosis & Wilson’s disease
Thyroiditis
Tissue resistance to PTH (pseudohypoparathyroidism)
hypoparathyroidism
clin man and cardiac findings (3)
Symptoms depend on the severity, duration and rate of development
Tetany (increased neuromuscularexcitability):
Mild:
Perioral numbness, muscle cramps/spasms, paresthesias, hyperreflexia
Severe:
Carpopedal spasms, laryngospasm, seizures
Defects affecting the teeth, nails, and hair
Cardiac findings
Prolonged QT interval, arrhythmias, hypotension
hypothyroidism
Chvostek sign
Contraction of the eye, mouth, or nose muscles elicited by tapping along the course of the facial nerve anterior to the ear
hypothyroidism
Trousseau sign
Spasm in the hand and wrist with compression to the forearm
Hypoparathyroidism
Lab findings
↓ PTH
↓ serum calcium
↑ serum phosphorus
hypoparathyroidism
EKG
Prolonged QT interval
Arrhythmias
hypoparathyroidism
Tx of acute severe symptomatic disease
With dosing
Calcium gluconate 1-2 g IV in 50 mL of 5% dextrose (or normal saline) infused over 10-20 minutes (preferred therapy)
Transition to oral calcium supplements
hypoparathyroidism
Tx for Mild symptomatic or chronic disease
Oral calcium supplements
Calcium carbonate(orcalcium citrate) 1,500-2,000 mg PO daily in divided doses
Recombinant human PTH
Tx of Vitamin D deficiency is the cause of hypocalcemia
Cholecalciferol (vitamin D3) – multiple dosing regimens
