Parathyroid

Question 1

How many parathyroid glands are there? Where are they located, and what do they secrete?

Answer 1

4 Parathyroid glands, located posterior to each pole of the thyroid

they secrete parathyroid hormone which regulates serum calcium

Question 2

Serum Calcium, What is it used for?

Answer 2

• Serum calcium is used for a lot of different things throughout the body
  
  • Critical in muscle contraction
    
    • terminal nuerons release Ca 2+ ions that bindo to activator proteins whcih signal muscles to contract and relax –> too little causes issues
  • Calcium is alos used as a stabilizer of the cardiac cell membranes against depolarization in severe hyperkalemia
  • Essential element of skeletal mineralization
  • bone is a reservoir for calcium
  • instrumental in blood clotting

Question 3

How does the body maintain Ca2+ homeostasis?

Answer 3

• Bones
  
  • Body senses low serum Ca2+
  • Parathyroid releases PTH
  • PTH stimulates osteoclasts to mobilize Ca2+ from the bones into the blood.
• Kidneys
  
  • Body senses low Ca2+
  • Parathyroid releases PTH
  • Kidenys respond by reducing Ca2+ clearence and stimulates 1.25-dihydroxyvitamin D
  • this stimulates Ca2+ absorption in the GI tract.
• Parathyroid glands
  
  • 4 pea sized glands on the posterior thyroid gland
  • secrete PTH which causes a rise in serum calcium levels
  • Parathyroid galnd responds to low or falling caclcium levels
  • Mobilizes calcium from bones by osteoclasts, and stimulates kidneys and gi tract to reabsorb calcium.

Question 4

DDX for hypercalcemia

Answer 4

The four parathyroid glands, located posterior to the thyroid gland, regulate calcium homeostasis through release of parathyroid hormone (PTH). Because most parathyroid disorders present with abnormalities of serum calcium, they commonly appear in differential diagnoses. Therefore, understanding the presentation and principles of evaluation of parathyroid disorders is important in primary care.

• Primary hyperparathyroidism
• Familial hypocalciuric hypercalcemia
• Lithium-associated
• Sarcoidosis
• Genetic disorders (e.g., multiple endocrine neoplasia, familial hyperparathyroidism)
• Renal failure acute or chronic Excess Vitamin D
• Granulomatous disease
• Williams syndrome
• Other endocrine diseases: thyrotoxicosis, adrenal insufficiency
• Milk-Alkali syndrome
• Thiazide diuretics
• Cancers (multiple myeloma, head, neck, and lung cancers, lymphoma)

Question 5

Negative feedback loop for calcium levels

Answer 5

An increase in blood calcium leads to an increase in secretion of calcitonin. Calcitonin works by stimulating osteoblast activity and decreasing osteoclast activity to bring more calcium into the bones

A decrease in blood calcium causes leads to secretion of PTH which causes osteoclast activity and causes bone breakdown and the release of calcium from the bones into the blood.

Question 6

Hyperparathyroidism definition/etiology, (remember facts), clincial features ,dx, tx, surgery?

Answer 6

• Elevated PTH and calcium levels (hypercalcemia) are present inhyperparathyroidism. It is the number one cause of hypercalcemia
• Benign parahyroid adenomas cause 80% of primary hyperparathyroidism and are the most common cause of asymptomatic calcium elevation in the blood
• Most common in women 3:1
• Incidence increases after age 50
• Hypercalcemia also found with renal failure, multiple myeloma, head and neck and lung chancers, sarcoidosis, TB, meds, lymphoma, adrenal insufficiency, and hyperthyroidism.

Remember

• The signs and symptoms of primary hyperparathyroidism is those of hypercalcemia
  
  • Summarized by stones bones abndominal groans, throans, and psychiatric overtones
  • Stones - kidney stones
  • bones - refers to bone related complicatoins. Examples of bone disease in hyperparathyroidism is osteiis fibrosa cystica, osteoporosis, osteomalacia, and arthritis
  • abdominal groans - refers to gi symptoms of n/v/d, and constipation. Can alos lead to PUD, pancreatitis
  • Thrones refers to polyuria and constipation
  • psychiatirc overtones - refers to effects on the CNS. Can include pscyh symptomrs - depression, memory loss, psychosis, delirium, fatigue.

clinical features

• Think mnuemonic but
• thirst, anorexia, nausea, vomiting, abdominal pain, constipation, fatigue, anemia, weight loss, PUD, pancreatitis, HTN

Diagnosis

• Often found with routine chemistry panel (elevated calcium)
• *Hallmark*** - adjusted total caclium is greater than 10.5mg/dl
  
  • Adjusted total Ca = measured serum calcium + 0.8 x (4.0 serum albumin)
• Elevated PTH
• Phosphate is usually low
• Imaging studies, - ultrasound, CT, MRI, and sestamibi scan
• EKG findings may show prolonged PR, shortened QT, bradycardia, heart block, and asystole.
• All patients should be screened for familial hypocalciuric hypercalcemia - a gene mutation that leads to elevated ca2+ levels.

tx

• Avoid meds/foods that increase calcium (thiazide diuretics, antacids, large doses of vit A and D)
• Increase fluids
• Activity
• Avoid immobilizatoin
• Monitor with schedule of serum calcium and albumin levels, kidney function, urinary calcium excretion, and bone density
• Treat hypercalcemic criss with IV fluids and biphosphonates
• Parathyroidectomy is indicated when sympotomatic primary disorder
  
  • aka adenoma of the parathyroid gland.

Surgery?

• Surgery is indicated if Serum Calcium is greater than 1mg/dL above the upper limit of serum Ca2+
• If creatine clearance is less than 60ml/m
• If bone mineral density T score is less than 2.5 @ hip, spine or wrist or previous fragility fracture
• Age younger than 50
• If you decide against parathyroidectomy you must monitor closely and check serum Ca2+ and creatinine levels annually
• Check bone density q 1-2 years.

Question 7

Hypoparathyroidism Def/cause, s/s, dx, tx

Answer 7

• Hypoparathyroidism is classified as decreased PTH
• Resultant in a low calcium level, increased phosphate levels
• Aquired most commonly after surgical removal of thyroid or parathyroid
• May be autoimmune, heavy metal toxicity, wilsons dz, hemochromatosis, thyroiditis, hypomagnesmia (alcoholism)
• DiGeorge Syndrome is congenital cause of low Ca arisign from parathyroid hypoplasia
• Congenitla pseudhypoparathyroidism

Clinical Clues as to cause of low PTH/low Calcium

• Acute illness: pancreatitis, tumor lysis, severe illness –
  
  • Results in secondary hyperparathyroidism from low circulating calcium levels
• Autoimmune disease
  
  • results in autoimmune parathyroid gland destruction
• family history of hypocalcemia
  
  • genetic defects in calcium sensing receptor or parathyroid hromone secretion
• Limited ultraviolet light exposure or poor dietary intake
  
  • vitamin D deficiency
• Malabsorption syndrome
  
  • vitamin D deficiency
• Neck surgery
  
  • low or absent parathyroid hormone with parathyroid gland removal
• renal disease
  
  • secondary hyperparathyroidism
• If calcium is low –> check parathyroid hormone levels, and phosphate levels.
  
  • Low PTH, high phosphorus –>
    
    • hypoparathyroidism
  • Normal PTH, elevated phosphorus –>
    
    • calcium sensing receptor activating mutation
  • Elevated PTH, elevated phosphorus –>
    
    • parathyroid hormone resistance (pseudohypoparathyrodisism)
  • Elevated PTH, low or normal phosphorus, low 25-vit D
    
    • vitamin D deficiency
  • elevated PTH, elevated phosphorus, low 1,25 vit d
    
    • chronic kidney disease

s/s

• Abdominal cramps
• muscle cramps
• tetany
• carpopedal spasm
• parasthesias
• Numbness/tinglign especially around mouth or in fingers
• hyperreflexia
• teeth, hair, and nail defects
• lethargy
• anxiety
• parkonsonism
• mental retardation
• blurred vision from cataracts
• personality changes
• bronchospasm
• seizures
• Cardiovascular
  
  • dyspnea, edema, palpitations, syncope
  • possible diagnosis: dysrhthmia, prolonged corrected QT interval, systolic dysfunction
• neurologic
  
  • headache, imparied vision, neuropsychiatric symptoms, possible diagnosis: premature cataracts, pseudotumor cerebri
• Neuromuscular
  
  • circumoral numbness and paresthesias; cramping, muscle twitching, spasms, seizures
  • possible diagnosis: carpopedal spasm

dx

1. Serum calcium, serum pth
2. chvostek sign
   
   1. contraction of the eye, nose, or mouth by tapping facial nerve anterior to the ear.
3. trousseau sign
   
   1. produces spams in the hand and wrist with compression to the forearm.
4. Hallmark
   
   1. low PTH
   2. low adjusted calcium
   3. increased phosphate
   4. EKG- may show prolonged QT, T wave abnormalities

treament

1. Treatment is directed at treating low calcium with Ca and Vit D supplements
2. Desired Ca level is 8.0-8.6mg/dl
3. Monitor adjusted serum Ca levels and Ca urine levels
4. avoid furosemide and toher meds that increase ca loss, may use thiazide diuretics innstead b/c they increase calcium
5. emergency treatment - iv calcium gluconate
6. PTH replacement only FDA approved in tx of osteoporosis, not hypoparathyrodism, in extreme cases may use teriparatide (recombinant PTH)