Calcium & bone problems Flashcards
How is parathyroid involved in calcium metabolism?
parathyroid hormone - maintains plasma calcium by direct actions on kidney, bone, and activating vit. D
How is bone involved in calcium metabolism?
calcium and phosphorous depot. Active tissue - an increase in calcium removal leads to bone loss
How is kidney involved in calcium metabolism?
~PTH affects calcium reabsorption/excretion at kidney.
~Activated vitamin D synthesis
How is PTH involved in calcium metabolism?
Maintains serum calcium.
~Increase calcium and phosphate reabsorption from bone.
~Increases calcium reabsorption at the kidney.
~Increase phosphate excretion from kidney.
~Stimulates conversion of vitamin D to active form
How is vitamin D involved in calcium metabolism?
25(OH)D3: storage
1,25(OH)2D3: active
How is calcium absorbed from the GI tract?
Absorption from the GI tract: Daily intake (≤ 200mg ≥ 1g) Passive absorption: Inefficient; only 10-20% absorbed passively Active absorption: Dependent on the active form of Vitamin D=[1,25(OH)2D].
What is the only reason to ever get a calcitonin test?
Elevated in Medullary Thyroid Carcinoma
Where is calcitonin made and what is its function?
- Produced from the C-cells of the thyroid.
* Inhibits osteoclast (bone resorbing cell) activity.
What other serum lab test do you need to get when you order a serum calcium?
albumin - most serum calcium is bound to albumin, not floating freely (ionized)
What is a common cause of secondary hyperparathyroidism?
vitamin D deficiency:
low vitamin D, PTH rises to try to compensate and stimulate calcium absorption; also mobilizes calcium from bone
Primary clinical effect: bone loss
What are the levels of PTH and calcium in primary hyperparathyroidism?
High PTH, High Ca2+
What is Chvostek’s sign?
twitching of the ipsilateral facial muscle when
the facial nerve is gently tapped
(hypocalcemia)
What are the neuromuscular symptoms of acute hypocalcemia?
– minor - paresthesias, numbness, tingling of the extremities
– major - carpal-pedal spasm, laryngospasm, seizures
What is Trousseau’s sign?
carpal spasm after the blood pressure cuff is
inflated above the systolic pressure for 2 minutes (hypocalcemia)
What medication can be used for hypocalcemia (besides calcium and vitamin D supplementation)?
thiazide diuretics - increase calcium reabsorption
What are some uncommon causes of hypercalcemia?
– Hyperthyroidism – Granulomatous disease (Sarcoid) – Drugs (lithium, aluminum intoxication, thiazide diuretics, vitamin D, vitamin A) – Immobilization – Milk-alkali Syndrome
What is the predominant presentation of Primary Hyperparathyroidism?
“asymptomatic” hypercalcemia
What are the clinical manifestations of primary hyperparathyroidism?
Site specific relative bone loss compared with age, sex matched controls
Distal radius > hip > spine
Fracture risk increased: radius and spine
What is the first treatment for hypercalcemia of malignancy?
Hydration! Volume depletion is a uniform manifestation
Familial Hypocalciuric Hypercalcemia is a benign condition.
T/F
True
Why is it important to distinguish FHH from primary hyperparathyroidism?
to avoid unnecessary parathyroidectomy
You should get xrays in patients at risk for osteoporosis in order to check for bone density.
T/F
False.
• Plain films do not measure bone density. Could be used to look for fractures.
• Bone density and therefore fracture risk are
best measured with bone densitometry
measurements (DXA, Q-CT, etc)
Indications for bone density test? (USPSTF)
~women aged 65 years or older
~younger women whose fracture risk is equal to or greater than that of a 65-year-old white woman who has no additional risk factors
~current evidence is insufficient to assess the balance of benefits and harms of screening for osteoporosis in men
A bone density test is sufficient to check for suspected osteoporosis.
T/F
False.
You must assess the other clinical risk
factors for BOTH bone loss and fracture as well as work up the metabolic factors.
