Parathyroid disorders - Endo

Question 1

Physio Overview

Answer 1

• Calcium and Phosphate Homeostasis
• 3 sites: intestine, kidney, bone
• 3 hormones: parathyroid hormone (PTH), calcitonin, calcitriol (active Vitamin D)

PTH
↑ renal Ca reabsorption, ↓ renal phos reabsorption, ↑ bone Ca and phos resorption (overall increased Ca and decreased phos levels)

Calcitonin (from thyroid)
↓ renal Ca and phos reabsorption (weak), ↓ bone Ca resorption

Calcitriol (aVitD)
↑ intestinal Ca absorption, ↑ renal Ca and phos reabsorption, ↑ bone Ca and phos resorption during hypocalcemia

• PTH ↑ serum Ca and ↓ serum phos
• Calcitonin ↓ serum Ca (“it tones down Ca”)
• aVitD ↑ serum Ca
• PTH and Calcitonin are opposites
• ↑ PTH = ↑ Ca and ↓ phos

Question 2

normal interplay

Answer 2

hypocalcemia stimulates

• ↑ PTH, which ↑ bone Ca resorption , ↑ renal Ca reabsorption and ↑ renal aVitD production
• ↑ aVitD ↑ intestinal Ca absorption

hypercalcemia stimulates
-↓ PTH, which ↓ bone Ca resorption (↑ bone mineralization), ↓renal Ca reabsorption (↑ renal Ca secretion) and ↓ renal aVitD production (which ↓ intestinal Ca absorption)

• too much PTH = hypercalcemia, hypophosphatemia
• too little PTH = hypocalcemia, hyperphosphatemia

Question 3

HYPERPARATHYROIDISM

Answer 3

Epidemiology
-1-4/1000, mc in >70yo Females, 10% familial

Etiology

• 1⁰ : 80% parathyroid adenoma, 20% hyperplasia, <1% carcinoma
• 2⁰ - the body normally responding to hypocalcemia, as in a Malabsorption Syndrome with subsequent 2⁰ hyperparathyroidism

1⁰: nl or ↑ PTH ↑ Ca
2⁰: ↑ PTH nl or ↓ Ca

Question 4

HYPERPARATHYROIDISM - pathophys

Answer 4

Physio

• Increase serum calcium concentration
• ↑ renal Ca reabsorption, ↓ renal phos reabsorption, ↑ bone Ca and phos resorption

Pathophysio

• ↑ PTH = hypercalcemia because more Ca is reabsorbed in the kidneys and more is leeched out of the bone = demineralization -> fx or bone cysts (osteitis fibrosa cystica)
• ↑ PTH = so much Ca ends up in the glomerular filtrate, that the kidneys can’t keep up reabsorbing it = hypercalciuria -> nephrolithiasis
• ↑ PTH = less kidney phos reabsorption = more phos into the urine = hyperphosphaturia and nl/hypophosphatemia

Question 5

HYPERPARATHYROIDISM - s/s

Answer 5

S/S

• hyperPTH is the mcc of hypercalcemia
• hyperCa usually found incidentally on routine chem panels
• mild hyperCa may be silent or have so little symptoms that they are only found on specific history questioning
• mild hyperCa = measured Ca < 12mg/dL, symptomatic hyperCa = measured Ca >12mg/dL
• hyperCa = adjusted total Ca >10.5 mg/dL
• adjusted Ca = corrected Ca = measured Ca + [0.8 x (4.0 - serum albumin)]

hypercalcemia symptoms = “Bones, Stones, (abdominal) Groans, (psychiatric) Moans, (fatigue) Overtones”

• bones: more trabecular/less cortical bone (thin cortex on XR), low bone density/demineralization -> bone pain and tenderness, arthralgias, fxs
• stones: calcium nephrolithiasis
• groans: abdominal pain (N/V/D/C)
• moans: depression, cognitive impairment (memory loss), psychosis, stupor…
• overtones: malaise, fatigue
• others: polyuria/polydipsia (hypercalciuria), cardiac (arrhythmias, heart block, HTN, athero progression), PUD, pancreatitis, neuro (paresthesias, weakness)

Question 6

HYPERPARATHYROIDISM - w/u, tx

Answer 6

W/U

• measured serum Ca, albumin, phosphate
• spot urinary Ca
• PTH assay
• bone density
• imaging not usually necessary unless planning surgery (dx is based on labs)

Tx

• if asymptomatic: monitor, keep active, drink adequate fluids, avoid immobilization, avoid thiazides and high doses of VitA and Ca-containing antacids, biannual serum Ca and albumin, annual BUN/Cr and urine Ca, bone density q2y
• if symptomatic (especially if kidney stones or bone disease): surgical parathyroidectomy

Question 7

HYPOPARATHYROIDISM

Answer 7

Etiology

• congenital
• acquired: post thyroidectomy or parathyroidectomies
• autoimmune: associated with other endocrinopathies
• associated with heavy metal disease (Wilson’s Dz = copper; Hemochromatosis = iron)
• concomitant with Mg deficiency

Question 8

HYPOPARATHYROIDISM - pathophys

Answer 8

Physio
-↑ renal Ca reabsorption, ↓ renal phos reabsorption, ↑ bone Ca and phos resorption

Pathophysio

• ↓ PTH = ↓ renal Ca reabsorption = ↑ Ca excretion = hypocalcemia and hypercalciuria
• ↓ PTH = more kidney phos reabsorption = less into the urine = hyperphosphatemia

Question 9

HYPOPARATHYROIDISM - s/s

Answer 9

hypocalcemia

• tetany, cramps, carpopedal spasm
• altered mental status, convulsions
• stridor
• perioral and distal extremity paresthesias
• Chvostek Sign: tapping on the facial n. gives facial m. contraction
• Trousseau phenomenon: carpal/digital spasm on inflating a BP cuff

Question 10

HYPOPARATHYROIDISM - w/u, tx

Answer 10

W/U

• measured Ca and albumin to get corrected Ca
• PTH assay
• EKG prolonged QT interval, T wave

Tx
-acute tetany with stridor may require emergency treatment: intubation, IV CaGluconate, PO Ca and VitD and Mg
-goal is serum Ca 8-8.5 mg/dL
i-f mild/asymptomatic, monitoring
-if chronic/symptomatic, then mainly po Ca and VitD
-recombinant PTH/teriparatide/Forteo, but very expensive
-monitor with serum Ca and spot urine Ca to keep at <30mg/dL