403 Parathyroid Flashcards by Medicine Katorse

Located posterior to thyroid gland

Four parathyroid glands

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Primary regulator of calcium physiology

Parathyroid hormone

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Where is calcium reabsorped

Distal tubule of kidneys

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Hormone that increases gastrointestinal calcium absorption

1,25 OH2 D

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Can suppress PTH secretion

Fibroblasts growth factor 3 (FGF3)

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Characterized by excess production of PTH by an autonomously functioning adenomas or hyperplasia

Hyperparathyroidism

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Cause of humoral hypercalcemia of malignancy

Overproduction of parathyroid hormone related peptide (PTHrP) secreted by cancer cells

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Primary function of PTH

Maintain extracellular fluid calcium concentration

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amount of calcium transferred between the ECF and bone each day

12 mmol or 500 mg of calcium

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crucial to the bone forming effect of PTH

Osteoblasts which have PTH/ PTHrP receptors

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strongly suppresses PTH gene transciption

1,25(OH)2D

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True or false. in patients with renal faillure, IV administration of supraphysiologic concentrations of 1,25(OH)2D or analogues dramatically suppresses PTH overproduction

True.

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normal range of PTH

1.9-2.0 nmol/L or 7.6- 8.0 mg/dL

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where does much of the proteolysis of the PTH hormone happen

liver and kidney

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syndrome that resembles primary HPT but without elevated PTH levels

humoral hypercalcemia of malignancy

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acts as an indirect antagonist to the calcemic actions of PTH

calcitonin

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what is the hypocalcemic activity of calcitonin

inhibition of osteoclast mediated bone resorption and secondarily by stimulation of renal calcium clearance

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major source of calcitonin

thyroid

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True or false. Cells involved in calcitonin synthesis arise from neural crest tissue

True.

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Therapeuticalyl 10-100 times more potent than mammalian forms in lower serum calcium

calcitonin from salmon

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account for 90% of all causes of hypercalcemia

parathyroid related, malignancy related, vitamin D related, associated with high bone turnover, associated with renal failure

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manifestation of hypercalcemia on ECG

short QT interval

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second most common cause of hypercalcemia in adult

malignancy

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interval between detection of hypercalcemia and death esp without vigorous treatement

interval between detection of hypercalcemia and death esp without vigorous treatment

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True or false. Differentiating primary hyperparathyroidism from occult malignancy can be occasionally difficult.

True.

True or false. Severe hypercalcemia is a medical emergency as it can lead to coma and cardiac arrest

True.

Classification of causes of hypercalcemia (5)

parathyroid related, malignancy related, vitamin D related, associated with high bone turnover, associated with renal failure

What level of serum calcium when symptoms appear

What is the serum calcium level for severe hypercalcemia

serum calcium more than 3.7- 4.5 mmol or 14.8- 18.0 mg/ dL

True or false. Parathyroid carcinoma are often aggressive.

False.

True or false. Manifestations of hyperparathyroidism involve primary the kidneys and skeletal system

True.

distinct bone manifestation of hyperparathyroidism

Pathognomonic features of osteitis fibrosa cystica

defined as biochemically confirmed hyperparathyroidism elevated or inappropriately normal PTH levels despite hypercalcemia with the absence of signs and symptoms typically associated with more severe hyperparathyroidism such as features of renal or bone disease

asymptomatic primary hyperparathyroidism

guidelines for surgery in asymptomatic primary hyperparathyroidism

serum calcium more than 1 mg/dl; CrCl less than 60 ml/min; bone density T score less than -2.5 at any of 3 sites; age less than 50 yrs old

guidelines for monitoring asymptomatic primary hyperparathyroidism

annually: serum calcium, serum creatinine, bone density; recommended: 24h urine calcium, creatinine clearance

definitive therapy for hyperparathyroidism

surgical excision of the abnormal parathyroid tissue

True or false. Serum calcium falls 24h after successful surgery and remain low normal for 3-5 days until remainin parathyroid tissue resumes full hormone secretion

True.

coexistent electrolyte imbalance must be considered because it can interferes with PTH secretion and causes functional hypoparathyroidism

hypomagnesemia

level of serum calcium associated with Chvostek and Trousseau's signs

serum calcium less than 2 mmol/L or less than 8 mg/dl

calcium infusion sufficient to correct hypocalcemia

0.5- 2 mg/kg per hour or 30-100 ml/ h of a 1 mg/ml solution

what should be added to calcium infusion is correction takes more than 2-3 days

vitamin D analoque and or oral calcium added

cost effective vitamin D analogue

Calcitriol 0.5-1 ug/ day for rapid onset action and prompt cessation when stopped

how if hypomagnesemia managed?

parenteral replacement 0.5-1.0 mmol/kg of body weight can be administered; total doses of 20-40 mmol are sufficient

used in the management of bipolar depression and other psychiatric disorders which causes hypercalcemia in 10% of treated patients

lithium

inherited as an autosomal dominant trait wherein affected individuals present with asymptomatic hypercalcemia

Familial benign hypercalcemia

rare autosomal domainant disorder caused by activating mutations in the PTH/PTHrP that lead to short limed dwarfism

Jansen disease

Treatment of hypercalcemia of malignancy

directed at control of tumor

among of vitamin D required to produce significant hypercalcemia

chronic ingestion 40-100 times the normal (amounts > 40,000- 100,000 U/d)

upper limit of dietary intake of vitamin D

2000 U/day

rare autosomal dominant disorder characterized by multiple congenital development defects including supravalvular aortic stenosis, mental retardation, and elfin facies in association with hypercalcemia due to abnormal sensitivity to vitamin D

William's syndrome or idiopathic hypercalcemia of infancy

which is more common in hyperthyroidism: hypercalcemia or hypercalciuria

hypercalciuria

rare cause of hypercalcemia caused by dieatary faddism

vitamin A intoxication

at what dosage of vitamin can lead to hypercalcemia

50,000-100,000 units of vitamin A daily (that's 10-20 times the minimum daily requirement)

important stimulus in the development of secondary hyperparathyroidism in renal disease

FGF23 dependent reduction in 1,25(OH)2 vitamin D; potent inhibitor of renal 1- alpha hydroxylase

evaluation of hypercalcemia. acute. PTH high

primary hyperparathyroidism consider MEN syndromes

evaluation of hypercalcemia. acute. PTH low

consider malignancy, PTHrP assay, clinical evaluation

evaluation of hypercalcemia. acute. PTH low. Negative malignancy

Granulomatous disease, FHH, milk alkali syndrome, medication, Vitamin A or D intoxication, adrenal insufficiencym hyperthyroidism

evaluation of hypercalcemia. chronic. PTH high

hyperparathyroidism consider MEN syndromes

evaluation of hypercalcemia. acute. PTH low

Granulomatous disease, FHH, milk alkali syndrome, medication, Vitamin A or D intoxication, adrenal insufficiencym hyperthyroidism

Management. Mild hypecalcemia. Less than 3 mmol/L or 12 mg/dL

hydration

Management, More sever hypercalcemia. 3.2 to 3.7 mmol or 13-15 mg/dL

decrease serum calcium 0.7-2.2 mmol/L (3-9 mg/dL) within 24-48 ours

antibody that blockls RANK ligand and reduce osteoclast number and function and approved therapy for osteoporosis

denosumab

how is pamidronate given in the treatment of hypercalcemia

30-90 mg pamidronate given as a single IV dose over a few hours

how is zolendorante given in the treatment of hypercalcemia

4 or 8 mg/5 min infusion

True or false. after 24 hr of use, calcitonin is no longer effective in lowering calcium

True.

acts on the osteoclasts to block bone resorption

calcitonin

usual dose of calcitonin

2-8 U/KBW IV, SC, or IM every 6-12 h

increased urinary calcium excretion and decrease intenstinal calcium absorption

glucocorticoids

treatment of choice for severe hypercalcemia which is difficult to manage medically

dialysis

True or false. Chronic hypocalcemia is less common than hypercalcemia

True.

Leads to transient hypocalcemia

severe sepsis, burns, AKI, extensive transfusions with citrated blood

True or false. Although half of patients in ICU have calcium concentrations of less than 2.1 mmol (less than 8.5 mg/dl), most do not have reduction in ionized calcium

True.

Medications that lead to transient hypocalcemia

protamine, heparin, glucagon