Calcium metabolism Flashcards
What is the explanation for hypercalcemia 90% of the time?
- Primary hyperparathyroidism
2. malignancy-secreting PTHrP
What is the most common form of primary hyperparathyroidism, producing hypercalcemia?
parathyroid adenoma
What is the second most common form of primary hyperparathyroidism?
parathyroid hyperplasia
Which types of malignancies can cause secretion of PTHrP and hypercalcemia?
small cell cancer (esp of lung)
renal cell carcinoma
breast mets to lung
multiple myeloma
10% of the time, what is the reason for hypercalcemia?
lots of Vit D ingested lots of Ca++ ingested Granulomas: macrophages activate Vit D. THink TB, sarcoidosis Increased bone turnover Thiazide diuretics
Which types of things can cause increased bone turnover–leading to hypercalcemia?
hyperthyroidism
Vit A intoxication
immobilization
Which diuretics increase calcium in blood, which decrease it?
Loops lose calcium. Thiazides retain it.
What are the signs/symptoms of hypercalcemia/hyperparathyroidism?
Stones, Bones, Groans, Psychiatric Overtones
What types of stones are produced by hypercalcemia?
Kidney stones (ca++)
nephrocalcinosis
polyuria, polydipsia
uremia
What types of bone issues do you see with hypercalcemia?
osteoporosis
osteitis fibrosa cystica
osteoarthritis
What are the features of osteitis fibrosa cystica?
subperiosteal bone respiration of the radial aspect of the middle phalanges tapering of the distal clavicle salt and pepper skull bone cysts brown tumors of the long bones
What are the abdominal groans of hypercalcemia?
constipation
N/V
peptic ulcers (increase in Ca++ causes an increase in gastrin)
pancreatitis
What are the psychiatric overtones of hypercalcemia?
lethargy
depression
psychosis
confusion, stupor, coma
What are other random features of hypercalcemia?
proximal muscle weakness
keratitis/conjunctivitis
HTN
itching
Which cells make parathyroid hormones?
chief/principal cells of parathyroid gland
What do the oxyphil cells of the parathyroid gland do?
no one knows!
they are packed with mitochondria, show up at puberty, and increase w/ age.
How does PTH stimulate bone turnover?
stimulates osteoblasts. They release RANKL that stimulates osteoclasts
Which carcinoma causes increased calcitonin?
medullary thyroid carcinoma
**not reactive to radioactive iodine treatments
C cells of thyroid aka parafollicular cells secrete calcitonin
What is the nerve supply to the parathyroid gland?
cervical sympathetic ganglion
controls blood flow, but not stimulation
What are the general causes of hypocalcemia?
Hypoparathyroidism
Vit D deficiency
acute pancreatitis
What are some common causes of hypoparathyroidism?
parathyroidectomy
autoimmune
pseudohypoparathyroidism (kidney doesn’t respond to PTH)
Di George Syndrome
Why does acute pancreatitis lead to hypocalcemia?
don’t get those fats dealt w/ w/o pancreatic secretions. Ca++ in gut combines w/ fatty acids–>soaps
Chovstek and Trouseau signs are seen w/ hypo or hypercalcemia?
hypocalcemia
What is a type of pseudohypoparathyroidism?
Type 1a: Albright Hereditary Osteodystrophy
What are the special features of Albright Hereditary Osteodystrophy?
short stature and obesity
underdeveloped 3rd and 4th phalanges
osteitis fibrosa cystica
Where are Ca++ and PO4 reabsorbed in the kidney?
Ca++–>DCT
PO4–>PCT
Describe the relationship b/w magnesium and PTH secretion?
Low Mg++ –>PTH secretion
Super Low Mg–>Decreased PTH secretion
What are some causes of low magnesium?
Maggie and her DADA diarrhea aminoglycosides diuretics alcohol
High PTH, High Ca++, Low phosphate…cause of hyperparathyroidism?
Primary hyperparathyroidism
most likely parathyroid adenoma
high PTH, Low Ca++, High phosphate…cause of hyperparathyroidism?
Secondary hyperparathyroidism
chronic renal failure, can’t reabsorb anymore!
*can also be caused by Vit D deficiency-may get rickets
What would the lab values and cause be for tertiary hyperparathyroidisM?
refractory chronic renal failure
parathyroid hyperplasia finally leads to a gland that secretes its own stuff constantly
High PTH, High Ca++
