Parathyroid diseases

Question 1

the inferior parathyroid glands arise from which branchial pouches?

Answer 1

3rd

Question 2

the superior parathyroid glands arise from which branchial pouches?

Answer 2

4th

Question 3

what is the predominant epithelial cell of the parathyroid gland, histologically?

Answer 3

chief cell

Question 4

which parathyroid gland cell has an eosinophilic granular cytoplasm?

Answer 4

oxyphil cell

Question 5

what are the cells of the parathyroid gland? which contain(s) PTH?

Answer 5

chief cell
oxyphil cell

both have PTH

Question 6

the gene for PTH production is located on which chromosome?

Answer 6

11

Question 7

what is the half life of PTH?

Answer 7

2-4 minutes

Question 8

what calcium receptor is what type of receptor?

Answer 8

GPCR

Question 9

what are the 3 target organs of PTH?

Answer 9

bone
intestinal mucosa
kidney

Question 10

how does PTH affect osteoclasts?

Answer 10

increases osteoclastic bone resporption of calcium and phosphate

Question 11

what is the effect of PTH on the kidney?

Answer 11

increases distal convoluted tubular calcium reabsorption and decreases proximal tubular phosphate reabsorption

Question 12

what is the net effect of PTH?

Answer 12

increased serum calcium

decreased serum phosphate

Question 13

PTH is responsible for fine tuning of calcium absorption in what part of the nephron?

Answer 13

distal nephron

Question 14

in which part of the nephron does PTH inhibit phosphate reabsorption?

Answer 14

proximal tubule

Question 15

in hyper PTH states, what is the effect on bicarb? why?

Answer 15

bicarb reabsorption is also impaired (inhibition of sodium / proton antiporter activity)

Question 16

what is the most common cause of hypercalcemia in ambulatory patients?

Answer 16

hyperparathyroidism

Question 17

what is the most common cause of hypercalcemia in hospitalized patients?

Answer 17

malignancy

Question 18

what is the first line test in hypercalcemic patients?

Answer 18

PTH levels

Question 19

what are the clinical features of primary hyper PTH disease?

Answer 19

BONES (long bone pain)
STONES (kidneys and polyuria, polydipsia)
GROANS (gastric ulcers)
MOANS (psychiatric - depression)

Question 20

what are the labs seen in primary hyper PTH disease?

Answer 20

• increased calcium
• decreased or normal serum phosphate
• increased or normal iPTH - INAPPROPRIATELY normal
• increased urine calcium

Question 21

primary hyper PTH tends to affect what type of bone? what is seen on X ray?

Answer 21

cortical bone

• “salt and pepper” skull
• osteitis fibrosa cystica (fibrous replacement of resorbed bone - bone pain, tenderness, deformity, fracture)

Question 22

what is the cure for primary hyper PTH disease? what does it require?

Answer 22

surgery

requires subtotal parathyroidectomy

Question 23

what is hungry bones syndrome?

Answer 23

surgical complication of primary hyper PTH disease

in patients with preexisting parathyroid bone disease the bones mop up calcium as the parathyroid drive ceases - causes acute hypocalcemia within 48 hours

Question 24

what is the medical therapy for primary PTH disease?

Answer 24

• avoid diuretics
• adequate hydration
• estrogen
• bisphosphonates
• calcimimetics
• monitor serum calcium

Question 25

what are the variants of hyperparathyroidism and their causes?

Answer 25

secondary (COMMON) - vitamin D deficiency, renal failure

tertiary - end stage renal disease, continuous parathyroid stimulation in secondary hyperparathyroidism as in renal failure leads to autonomous parathyroid glands

Question 26

what is the cause for familial hypocalciuric hypercalcemia (FHH)? what do the labs look like?

Answer 26

• inactivating mutation in calcium sensor / receptor (parathyroids and kidneys)
• labs: mild hypercalcemia and normal or elevated iPTH

Question 27

what are the causes of hypo PTH - decreased PTH production?

Answer 27

• surgical excision
• infiltrative process - wilsons, hemochromatosis
• autoimmune destruction
• congenital - DiGeorge, defective branchial arch formation
• decreased magnesium - impairs PTH secretion and action
• familial

Question 28

symptoms of hypo PTH

Answer 28

• paresthesiae, carpopedal spasm, tetany, laryngeal stridor, convulsions, apathy, depression
• calcification of basal ganglia on brain CT and benign intracranial hypertension
• GI: nausea, vomiting, abdominal pain, malabsorption
• cardiac: prolonged QT interval on ECG
• cataracts, alopecia
• mucocutaneous candidiases in DiGeorge

Question 29

effects of hypoparathyroidism

Answer 29

• low mobilization of calcium from bone
• low renal distal tubular calcium reabsorption
• low renal phosphate excretion
• low renal production of 1,25 diOH vitamin D
• low calcium and high phosphate
• low PTH or inappropriately normal

Question 30

in diagnosing hypocalcemia what is important to remember in order to confirm true low calcium?

Answer 30

correct for serum albumin

Question 31

treatment for hypocalcemia

Answer 31

• IV calcium gluconate or PO calcium carbonate

- vitamin D3 (calcitriol or similar) PO twice daily

Question 32

what is NATPARA? what are its benefits?

Answer 32

synthetic PTH analog

• decreases risk for kidney stone formation
• decreases risk for bone demineralization
• decreases pill burden on patients with hypoparathyroidism

Question 33

what is the pseudo hypoparathyroidism? what are the clinical features / labs?

Answer 33

end organ resistance to PTH due to receptor or post receptor defect

hypocalcemia, hyperphosphatemia, HIGH PTH