PANCE Blueprint Endocrinology (7%)

Hypoparathyroidism (Lecture)

Patient will present as → a 39-year-old woman after total thyroidectomy for papillary carcinoma of the thyroid is noted to have carpal spasm when her blood pressure is taken and facial muscle contractions with tapping over the facial nerve. You also note increased deep tendon reflexes along with perioral paresthesia. Lab work reveals decreased serum calcium, decreased parathyroid hormone, and elevated serum phosphate. On EKG there is a prolongation of the QT interval

Hypoparathyroidism will present with a decreased parathyroid hormone (↓ PTH). This causes calcium levels in the blood to decrease

  • Hypoparathyroidism is rare, you are much more likely to be tested on hyperparathyroidism
  • The two most common etiologies are postsurgical (damage from neck or thyroid surgery) or autoimmune
    • Accidental damage/removal of parathyroid during neck/thyroid surgery
    • Autoimmune destruction of the thyroid gland

Patients will show signs of neuromuscular irritability with carpopedal spasm, laryngeal spasm, tingling, tetany, and facial grimacing.

Diagnosis is made by the triad: ↓ Ca+, ↓ PTH, and ↑ phosphate

  • Why the low serum calcium? Calcium is low because the gland cannot secrete PTH (hence a low PTH) and PTH is responsible for the reabsorption of calcium from the bones, kidneys, and GI tract. Because you can't reabsorb calcium, your calcium will be low.
  • Why the elevated phosphate? PTH normally inhibits the reabsorption of phosphate by the kidney. Therefore, without enough PTH there is more reabsorption of the phosphate leading to a high phosphate level in the blood.
  • EKG = Prolonged QT

The following are signs of hypocalcemia:

  • Chvostek's sign (watch video) is the twitching of the facial muscles in response to tapping over the area of the facial nerve
  • Trousseau's sign (watch video) is carpopedal spasm caused by inflating the blood-pressure cuff to a level above systolic pressure for 3 minutes
  • ↑ DTRs and carpopedal spasms

Chvostek's sign is seen in patients with hypocalcemia secondary to low PTH secretion

Immediate: vitamin D and calcium to bring calcium levels back to normal

  • Tetany - secure airway, IV calcium gluconate
  • Long term: recombinant human parathyroid hormone to make up for bodies underproduction

osmosis Osmosis


Hypoparathyroidism is an uncommon condition characterized by a low level of parathyroid hormone (PTH). Often caused by “accidental” removal of the parathyroid glands during thyroid surgery. Other causes of parathyroid deficiency include tumors and heavy metal poisoning. Treatment consists of taking supplements to normalize calcium and phosphorus levels.

Play Video + Quiz

Parathyroid Gland Overview


The parathyroid gland is a series of four small glands located in the neck on the rear surface of the thyroid gland. It serves primarily in calcium homeostasis and has a blood calcium sensor that detects when blood calcium levels are abnormally low. It responds by releasing parathyroid hormone (PTH) which stimulates osteoclasts into action. Osteoclasts resorb bone and release a large amount of calcium. This calcium enters the blood and results in increased blood calcium levels. PTH can also activate vitamin D by promoting the activity of an enzyme that converts inactive vitamin D to active vitamin D

Play Video + Quiz

Question 1
A 65-year-old woman with a seizure disorder controlled with phenytoin presents to your office complaining of muscle cramps, dry skin, and depression. Examination shows carpal-pedal spasms after application of a blood pressure cuff. The most likely diagnosis is  
Hyperventilation with panic attacks
Question 1 Explanation: 
Hypocalcemia is defined as a decrease in total plasma calcium concentration < 8.8 mg per dL in the presence of normal plasma protein concentration. Causes include hypoparathyroidism, vitamin D deficiency, renal tubular disease, magnesium depletion, acute pancreatitis, hypoproteinemia, septic shock, hyperphosphatemia, and drugs, including phenytoin, phenobarbital, and rifampin. Most patients are asymptomatic. Symptoms, when present, include muscle cramps involving the legs and back, mental status changes, dry skin, depression, and psychosis. Papilledema may occasionally occur, and cataracts may develop after prolonged hypocalcemia. Severe hypocalcemia (< 7 mg per dL) may cause tetany, laryngospasm, or generalized seizures. With hypocalcemia giving rise to latent tetany, the patient may exhibit a positive Chvostek’s sign (involuntary twitching of the facial muscles caused by a light tapping of the facial nerve just anterior to the exterior auditory meatus) or a positive Trousseau’s sign (carpopedal spasm caused by reduction of the blood supply to the hand with a blood pressure cuff inflated to 20 mm Hg above the systolic BP applied to the forearm after 3 minutes). Hypocalcemia can cause heart block and arrhythmias. ECG changes show prolongation of the QTc and ST intervals. T-wave peaking or inversion can also occur. Severe hypocalcemic tetany is treated initially with intravenous infusion of calcium salts (calcium gluconate). In chronic hypocalcemia, oral calcium and vitamin D supplements are usually sufficient. Treatment of hypocalcemia in patients with renal failure must be combined with dietary phosphate restriction and phosphate-binding agents such as calcium carbonate to prevent hyperphosphatemia and metastatic calcification.
There is 1 question to complete.
Shaded items are complete.

References: Merck Manual · UpToDate

Hyperparathyroidism (Prev Lesson)
(Next Lesson) Pituitary Disorders (PEARLS)
Back to PANCE Blueprint Endocrinology (7%)

The Daily PANCE and PANRE

Get 60 days of PANCE and PANRE Multiple Choice Board Review Questions delivered daily to your inbox. It's 100% FREE and 100% Awesome!

You have Successfully Subscribed!