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.
- Muscular changes with hypoparathyroidism will be the opposite of those with hyperparathyroidism.
- Chvostek's sign (watch video): Tap of facial nerve elicits cheek twitch
- Trousseau's sign (watch video): BP cuff inflation elicits carpal spasm
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 |
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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 + QuizParathyroid 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
Question 1 |
Hypothyroidism | |
Hyperventilation with panic attacks | |
Hyperkalemia | |
Hypocalcemia | |
Hyponatremia |
References: Merck Manual · UpToDate
