Lecture 11 - Calcium and Vitamin D Flashcards
How does the parathyroid play a role in calcium and vitamin D homeostatsis?
Parathyroid secretes parathyroid hormone when it senses low Ca2+
this parathyroid hormone converts 25, Vit D to 1,25 Vit D
How do you correct calcium?
Measured calcium + 0.8(4-albumin)
normal albumin is 4
you’re doing this because when you measure calcium you are only measuring the free/ionized and you need to account for how much is bound to albumin
basically if you have low calcium correct for the low albumin
What are the physiological causes of hypocalcemia?
failure to secrete PTH resistance to PTH failure to produce 1,25 Vit D Resistance to 1,25 vit D calcium complexation or deposition
Albright’s hereditary osteodystrophy
autosomal dominant pseudohypoparathyroidism
resistance to PTH
short stature short neck short digits (brachydactylyl) round face
Chvostek’s sign
see with hypocalcemia
when you tap the facial nerve there is twitching
Trousseau’s sign
seen with hypocalcemia
inflate the BP cuff 20 mmHg above systolic BP and wait 3 minutes – you’ll see carpospasm
What are the signs and sxs of hypercalcemia?
Bones
- osteoporosis
- arthritis
- osteitis fibrosa
Stones (renal)
- kidney stones
- polyuria
Moans (CNS)
- lethargy
- depression
- psychosis
- stupor
- coma
Groans (GI)
- constipation
- N/V
Which test will help you narrow you differential dx for a pt with hyperglycemia?
serum parathyroid hormone (PTH)
Hypercalcemia can be split into two main categories, what are they?
PTH dependent or PTH independent
dependent:
- primary
- familial hypercalemia hypocalciuria
- lithium use
independent:
- malignancy
- medications- thiazide diuretics, vitamin A intoxication, vitamin D intoxication
- hyperthyoridism
- renale failure
What is the most common form of primary hyperparathyroidism?
adenoma (85% - one gland)
Who gets hyperparathyroid surgery?
<50 y/o
very high calcium level >11.5
symptomatic - kidney stone
decreased bone density
What is the pathway of vitamin D?
sun activates it in the skin before it goes to the liver where it meets up with other vitamin D from the diet
then it goes to the kidney where it changes from 25, D to 1,25D before going to the bone and intestines
in the intestine it increases calcium and phosphorus absorption
in the bone in mobilizes calcium stores
Secondary hyperparathyroidism commonly caused by?
low vitamin D –stimulating high PTH
What decreases your ability to make vitamin D?
old age
darker skin
living where there isn’t much sun
When is vitamin D toxicity?
hypercalcemia
d/t sxs: nausea, dehydration, and lethargy
> 40,000 IU/day
What three hormones regulate calcium levels?
Parathyroid hormone
calcitirol
calcintonin
What does PTH do to phosphate?
inhibit its reabsorption
Primary hyperparathyroidism
typically presents asymptomatic on labs with hypercalcemia
MC cause is adenoma (80%)
15% hyperplasia
How can you distinguish parathyroid adenoma from hyperplasia?
Technetium sestamibi scan
focal retention = adenoma
For primary parathyroidism, who gets parathyroidectomy?
Guidelines if they meet the follow criteria:
- <50 years
- serum Ca2+ >1mg/dl above UNL
- T score
If a pt with primary parathyroidism can’t get surgery, what can you give them to lower their calcium?
calcimimetic (cinacalcet)
you’ll also give them bisphosphonate to improve bone mineral density
Secondary hyperparathyroidism
increase PTH d/t hypocalcemia or vitamin D deficiency
Chronic kidney failure is the MC cause of secondary
-kidneys convert vitamin D to its active form
What is the triad for primary hyperparathyroidism?
hypercalcemia
increase PTH
decrease phosphate
What is the triad for hypoparathyroidism?
hypocalcemia
decrease PTH
increase phosphate
