Disorders of Calcium and Parathyroid Gland

Question 1

How is calcium distributed in the serum?

Answer 1

40% protein bound
10% complexed (citrate or phosphate ions)
50% ionized

Question 2

What form of Ca is free and bioavailable?

Answer 2

ionized

Question 3

Clinically, what is measured to determine Ca level?

Answer 3

total serum Ca

Question 4

How does PTH affect bone?

Answer 4

increased Ca mobilization

Question 5

How does PTH affect the kidneys?

Answer 5

increases calcium reabsorption from DCT

Question 6

How does PTH affect intestines?

Answer 6

indirectly enhances the absorption of calcium by increasing the production of activated vitamin D

(up-regulates 1-alpha-hydroxylase)

Question 7

What enzyme activates vitamin D?

Answer 7

1-alpha-hydroxylase

Question 8

Where is Ca-sensing R found?

Answer 8

parathyroid
kidney
C cells of thyroid
bone

Question 9

Stimulation of Ca-sensing receptor results in:

Answer 9

intracellular cascade to decrease PTH secretion

Question 10

What is the appropriate workup for hypercalcemia?

Answer 10

1. check albumin and total Ca TWICE

2. check PTH

Question 11

PTH dependent causes of hypercalcemia?

Answer 11

1. hyperparathyroidism
2. familial hypocalciuric hypercalcemia
3. medication induced

Question 12

PTH independent causes of hypercalcemia?

Answer 12

1. tumor induced
2. granulomatous diseases
3. multiple myeloma
4. hyperthyroidism or adrenal failure
5. medication induced

Question 13

What meds may cause PTH-related hypercalcemia?

Answer 13

Li, HCTZ

Question 14

What meds may cause PTH-unrelated hypercalcemia?

Answer 14

vit D toxicity
vit A
milk-alkali

Question 15

80-85% of primary hyperthyroidism is caused by:

Answer 15

adenoma

Question 16

What is the appropriate lab workup for primary hyperparathyroidism?

Answer 16

1. Ca, albumin
2. PTH
3. 25-OH vitamin D
4. 24h urine Ca, to differentiate from FHH

Question 17

What are appropriate imaging studies for primary hyperparathyroidism?

Answer 17

1. thyroid US
2. Tc-sestamibi scan
3. DXA

Question 18

What causes familial hyperparathyroidism?

Answer 18

inactivating mutation of CaSR, with 100% penetrance

*note: the mutation in present in the parathyroid and kidneys, which causes calcium retention

Question 19

What lab abnormalities are expected in familial hyperparathyroidism?

Answer 19

mildly increased serum Ca, hypocalciuria, slight elevation in PTH

Question 20

What is the trx for familial hyperparathyroidism?

Answer 20

none

Question 21

Results from long-standing secondary hyperparathyroidism:

Answer 21

tertiary hyperparathyroidism

Question 22

Most common malignancies causing hypercalcemia?

Answer 22

breast and sq cell carcinoma

also causes by lung, lymphoma, thyroid, kidney, prostate, multiple myeloma, pancreas…

Question 23

What are causes of hypercalcemia in malignancy?

Answer 23

1. suppression of PTH due to PTH-related protein (which binds to common receptor)
2. bony mets or bone destruction
3. activation of osteoclasts by cytokines/TNFalpha

Question 24

What is the initial treatment for acute hypercalcemia?

Answer 24

1. Address volume status**
2. saline diuresis +/- furosemide (once volume status corrected)
3. calcitonin
4. bisphosphonates

Question 25

What hypercalcemic patients would be treated with steroids?

Answer 25

myeloma, granulomatous disease and vit D toxicity **inhibit 1-alpha-hydroxylase

Question 26

Major causes of secondary PTH elevation:

Answer 26

1. hypocalcemia 2. hyperphosphatemia 3. vit D deficiency

Question 27

Clinical signs of hypocalcemia:

Answer 27

1. agitation 2. hyperreflexia 3. convulsions 4. HTN 5. long QT

Question 28

Causes of low PTH hypocalcemia?

Answer 28

hypoparathyroidism Mg deficiency phosphate excess

Question 29

Causes of high PTH hypocalcemia?

Answer 29

Severe vit D deficiency renal failure resistance to vit D or PTH

Question 30

In acute hypocalcemia, always correct: | in addition to the low Ca, duh

Answer 30

low Mg (if present) *treat low Ca with Ca gluconate

Question 31

Long term management of hypocalcemia?

Answer 31

1. oral Ca salts 2. vit D 3. HCTZ (increases reabs of Ca in distal tubule)

Question 32

What is MEN?

Answer 32

AD syndrome characterized by 2 or more endocrine tumors; may be benign or malignant and functional or non-functional

Question 33

Where do tumors present in MEN1

Answer 33

1. parathyroid 2. pancreas 3. pituitary

Question 34

What are signs/symptoms of MEN1?

Answer 34

kidney stones, recurrent peptic ulcers, fasting hypoglycemia, hypogonadism, galactorrhea

Question 35

What labs would be abn in MEN1?

Answer 35

``` gastrin Ca/PTH insulin/glucose PRL IGF-1 ACTH/cortisol ```

Question 36

What are the average ages for the following MEN1 tumors: - -pituitary - -insulinoma - -gastrinoma

Answer 36

38 25 35

Question 37

How does a parathyroidectomy affect patients with primary hyperparathyroidism and gastrinoma?

Answer 37

improves hypercalcemia | decreases gastrin

Question 38

Important clinical features of MEN2B?

Answer 38

1. mucosal neuromas (~100%) 2. marfanoid habitus 3. pheochromocytoma 4. medullary thyroid carcinoma (~100%)

Question 39

What gene is affected in MEN2?

Answer 39

RET

Question 40

Epidemiology of: MEN1 MEN2A MEN2B

Answer 40

``` MEN1 = 2nd-3rd decade MEN2A = adults MEN2B = early onset ```

Question 41

Important clinical features of MEN2A?

Answer 41

1. medullary thyroid carcinoma (~100%) 2. pheochromocytoma 3. primary hyperparathyroidism

Question 42

MEN2B is associated with MORE malignant: | compared to 2A

Answer 42

medullary thyroid carcinoma

Question 43

Signs/symptoms of MEN2A and MEN2B

Answer 43

thyroid nodules, HTN, "spells", diaphoresis

Question 44

Abn labs in MEN2A and MEN2B

Answer 44

1. calcitonin, CEA 2. plasma and urine metanepherines 3. chromogranin A

Question 45

Definitive treatment of MEN2A and MEN2B

Answer 45

thyroidectomy with lymph nose dissection