Endocrinology

Question 1

Pearl - Calcium physiology: in parathyroid-mediated process, serum Ca and PO4 for in ____ direction

Answer 1

Opposite
- HyperPTH: High Ca, Low PO4
- HypoPTH: Low Ca, High PO4

Question 2

Pearl - Calcium physiology: in a vitamin D mediated process, serum calcium and phosphate go in ____ direction

Answer 2

Same

• Osteomalacia: Low Ca, Low PO4
• Vit D excess: High Ca, High PO4

Question 3

Pearl - Calcium physiology: when Ca, PO4, PTH all high, think ____ [etiology]

Answer 3

Kidney: reduced ability to excrete phosphate
- Tertiary hyperPTH [in longstanding CKD]

Question 4

Pearl - Calcium physiology: which electrolyte can reduce PTH secretion and cause PTH resistance?

Answer 4

Hypomagnesemia: therefore, low Mg in someone with apparent hypoPTH [or inappropriately normal PTH]

Question 5

Primary HPTH - when do you send someone for surgery?

Answer 5

1. Symptomatic = surgery!
2. Asymptomatic = Stay The Fudge Away U Studpid Calcium
   - Serum total calicum >0.25 above ULN
   - Fractures [vertebral only, by XR, CT, MRI, VFA]
   - Age <50
   - Urine Ca >6.25 [>250mg/d] in women or >7.5 [>300mg/d] in men
   - Stones or nephrocalcinosis by XR, US, CT
   - CrCl <60 [stage 3 CKD]

Question 6

Primary HPTH - if NOT candidate for surgery, what is part of medical management?

Answer 6

• Daily calcium intake [1000-1200mg]
• Correct Vitamin D deficiency [25-OH vitD >75]
• Bisphosphonates or Prolia [effective at increasing BMD]
• Cinacalcet [effective at reducing serum calcium and should be considered in symptomatic PHPT if surgery not option - may combine with BP/Prolia]

Question 7

Primary HPTH: was is part of monitoring if NO surgery?

Answer 7

1. Serum Ca, 25-OH Vit D: annually
2. Skeletal monitoring:
   - 3-site DXA scan q.1-2 years [hi[, lumbar, distal 1/3 radius]
   - Vertebral XR or vertebral # Ax [VFA] if indicated [to look for #]
3. Renal monitoring: CrCl annually +/- abdo [XR, CT, US] if indicated

Question 8

In PTH-mediated hypercalcemia, which test should always be done to rule out which diagnosis before sending someone for surgery?

Answer 8

1. Urine calcium
2. Rule out FHH
   - FHH: UCa low, SCa high [UCa:Cr usually <0.01]
   - HPTH: UCa high, SCa high [UCa:Cr usually >0.02]

Question 9

Secondary/Third HPT: briefly explain pathophysiology

Answer 9

• Appropriate increase in PTH in face of hypoCa or vit D deficiency [most common]
• PTH working appropriately to absorb all urine Ca/salvage Ca level

Question 10

In secondary/third HPT, what are 2 conditions where mineral replacement [Ca, Vit D] should be replaced in a specific fashion?

Answer 10

Post-gastric bypass
- CANNOT use calcium carbonate as supplement, no acidity to absorb this; use calcium citrate

CKD
- Treat with calcitriol, phosphate restriction, non-Ca phosphate binders
- Cinecalcet

Question 11

Indications for surgery in tertiary HPT?

Answer 11

• Refractory hyperPTH despite Vit D/calcimimetics [no absolute #/PTH cutoff, KDIGO defines as PTH still rising, symptomatic]
• HyperCa severe/symptomatic
• Calciphylaxis
• Progressive bone disease

Not lots og guidance here largely b/c no high quality RCTs showing difference in outcome of medical vs. surgical therapy in this population

Question 12

Diagnosis of hypoparathyroidism?

Answer 12

• Hypocalcemia
• Undetectable, low, or inappropriately normal PTH [measured on 2 occasions >2 weeks apart]
• Supported by high PO4, low 25-OH Vit D
• Permanent postsurgical hypoPTH is defined as persisting >12 months post-op

Question 13

Management of hypoparathyroidism?

Answer 13

• 1st-line: conventional therapy w/ oral Ca, calcitriol
• PTH therapy can be considered if conventional therapy insufficient

Question 14

DDx: hypoparathyroidism

Answer 14

Aquired:
- HypoMg: PTH resistance
- HyperMg: reduce PTH synthesis/secretion
- Post-surgical [common] or post-rads
- Infiltrative [sarcoid, amyloid, cancer mets]
- Autoimmune polyglandular syndrome type 1 [APS-1]: Whitaker’s triad (chronic mucocutaneous candidiasis, Addison’s, hypoPTH - AIRE mutation)

Congenital:
- Pseudohypoparathyroidism [genetic mutation in GNAS gene]
- DiGeorge Syndrome / 22q11.2 deletion syndrome: parathyroid agenesis
- Note: hypoCa outside of hypoPTH can occur in extravascular sequestration [hyperPO4, pancreatitis, osteoblastic mets]

Question 15

MEN [Multiple Endocrine Neoplasms]
- Inheritance pattern?
- Associations? [MEN1, MEN 2A-B]

Answer 15

1. All autosomal dominant
2. MENs:
   - 1 [PPP]: parathyroid, pancreas, pituitary
   - 2A [PMP]: parathyroid, thyroid, pheo
   - 2B [MMP]: marfanoid/mucosal neuromas, thyroid, pheo