3. MTB Step 3 - Calcium Disorders Flashcards
Cards Complete:
HYPERCALCEMIA
What is the Most Common Cause of Hypercalcemia in outpatients, by far?
The most common cause of Hypercalcemia in outpatients, by far, is Primary Hyperparathyroidism.
- An enormous number of people are walking around with hyperparathyroidism with no symptoms.
HYPERCALCEMIA
What are (9) Other causes of Hypercalcemia, in addition to the most common cause?
- Malignancy: Produces a parathyroid hormone–like particle
- Granulomatous disease: Sarcoid granulomas actually make vitamin D
- Vitamin D intoxication
- Thiazide diuretics: These increase tubular reabsorption of calcium
- Tuberculosis
- Histoplasmosis
- Berylliosis: Forms granulomas
- Lithium
- Vitamin A toxicity
HYPERCALCEMIA
BASIC SCIENCE CORRELATE
What is the Mechanism of Parathyroid Hormone (PTH) Effect?
Mechanism of Parathyroid Hormone (PTH) Effect
- Reabsorbs Calcium at the Distal Tubule
- Excretes Phosphate at the Proximal Tubule
- Activates Vitamin D from 25 ⇒ 1,25 Dihydroxy form
- Reabsorbs both Calcium and Phosphate from Bone
HYPERCALCEMIA
How do the vast majority of Hyperparathyroidism cases present?
The vast majority of cases present as Asymptomatic Hypercalcemia
HYPERCALCEMIA
What are (4) Target Organ Damage manifestations of Hyperparathyroidism?
Target Organ Damage is as follows:
- Kidney stones
- Osteoporosis/Osteomalacia/Fractures
- Confusion
- Constipation and Abdominal Pain
HYPERCALCEMIA
BASIC SCIENCE CORRELATE
What is the Mechanism of Neural Inhibition in Hypercalcemia?
Mechanism of Neural Inhibition in Hypercalcemia
High calcium levels make it harder for excitable tissue such as nerves to depolarize. High calcium moves the threshold for depolarization away from the resting membrane potential. Bowels are a long muscular tube. High calcium inhibits smooth muscle contraction.
Low calcium = Hyperexcitable
HYPERCALCEMIA
What are the Diagnostic Test findings for Hyperparathyroidism?
- Elevated PTH
- Hypercalcemia
HYPERCALCEMIA
When are Sestamibi and Nuclear Imaging the correct answer for Hyperparathyroidism?
Sestamibi allows proper localization of adenomatous gland. Since 80 percent of Hyperparathyroidism arises from a solitary adenoma, scanning is the answer:
It tells you which gland to remove
HYPERCALCEMIA
What is the Treatment for Hyperparathyroidism?
Surgical Removal
Remember: Hyperparathyroidism may be a part of multiple endocrine neoplasia (MEN) syndrome.
HYPERCALCEMIA
What are the nature of cases with Hyperparathyroidism?
The nature of cases is as follows:
- Solitary adenoma: 80 percent
- Four-gland hyperplasia: 19 percent
- Cancer: 1 percent
HYPERCALCEMIA
When is the answer to a question about hyperparathyroidism surgical removal of the parathyroid gland?
Answer: Remove the gland under any of the following circumstances:
- Any symptomatic disease (“stones, bones, psychic moans, GI groans”)
- Renal insufficiency, no matter how slight
- Very elevated serum calcium (> 12.5)
- Age < 50
- Osteoporosis
HYPERCALCEMIA
How does Acute, Severe Hypercalcemia present?
This condition presents with the following:
- Confusion
- Constipation
- Polyuria and polydipsia from nephrogenic diabetes insipidus
- Short QT syndrome on the EKG
- Renal insufficiency, ATN, kidney stone
HYPERCALCEMIA
What are (5) Medical treatments used for Acute, Severe Hypercalcemia?
- Hydration: High volume (3–4 liters) of normal saline
- Bisphosphonate (pamidronate or zoledronate) is very potent but slow, taking a week to work. It inhibits osteoclasts.
- Furosemide: Only after hydration has been given. Loop diuretics increase calcium excretion by the kidney if urine is not being produced through hydration alone.
- Calcitonin: If hydration and furosemide do not control the calcium and you need something faster than a bisphosphonate, then calcitonin is the answer.
- Steroid: Use if the etiology is granulomatous disease.
HYPERCALCEMIA
BASIC SCIENCE CORRELATE
What is the Mechanism of Volume Depletion in Hypercalcemia?
Mechanism of Volume Depletion in Hypercalcemia
High calcium levels inhibit the effect of ADH on the collecting duct, inducing nephrogenic diabetes insipidus. High calcium filtration also promotes osmotic diuresis.
HYPOCALCEMIA
What are (7) possible causes of Hypocalcemia
Hypocalcemia may be caused by the following:
- Surgical removal of parathyroid glands
- Hypomagnesemia: Magnesium is needed to release PTH from the gland.
- Vitamin D deficiency
- Acute hyperphosphatemia: Phosphate binds with the calcium and lowers it.
- Fat malabsorption: This binds calcium in the gut.
- PTH resistance: Pseudohypoparathyroidism that accompanies short fourth finger, round face, and mental retardation
- PPIs: PPIs can decrease calcium and magnesium absorption
