Secondary and Tertiary Hyperparathyroidism Flashcards
(27 cards)
Secondary Hyperparathyroidism
most commonly due to
-chronic kidney disease
-vitamin D deficiency
-intestinal calcium malabsorption.
How to Tx Hypocalcemia and Vit D
Patients should receive 1000 to 1200 mg of calcium per day
vitamin D supplementation to maintain a serum 25(OH)D of more than 30 ng/mL.
Causes of secondary hyperparathyroidism
Celiac disease, Cystic fibrosis, Short gut syndrome
Bariatric procedures
Medications
Lithium, Diuretics (e.g., hydrochlorothiazide, furosemide)
Metabolic abnormalities
Hypermagnesemia. Hyperphosphatemia
Congenital disorders
Transient neonatal hyperparathyroidism
DiGeorge syndrome
chronic renal failure
> > reduced phosphate excretion
increased serum phosphate, which binds to calcium and reduces serum-free calcium levels
reduced 1-hydroxylase activity in the kidney, which results in decreased renal conversion of 25 (OH) vitamin D to 1, 25, (OH)2 vitamin D
decreased intestinal absorption of calcium
This can cause what ?
(1) down-regulation of the CaSR
(2) down-regulation of the vitamin D receptor on parathyroid cells
(3) alterations in cell cycle regulation—
all leading to PTH hypersecretion, parathyroid cell proliferation, and parathyroid gland hyperplasia
Tx
- dietary phosphate reduction
- phosphate binders
- oral calcium
- calcitriol supplementation
- intravenous vitamin D analogues
- dialysis.
cinacalcet, a calcimimetic agent, is used to alter the sensitivity of the CaSR of the parathyroid cells and reduce PTH secretion
indications for parathyroidectomy in patients with renal HPT:
(1) a PTH greater than 800 pg/mL
(2) sustained hypercalcemia
(3) refractory hyperphosphatemia
(4) elevation of calcium-phosphorous product greater than 55 mg2/dL
(5) severe symptomatic bone disease
(6) calciphylaxis
symptomatic ectopic extraosseous calcification (calcinosis)
intolerance to cinacalcet
profound muscle weakness
and intractable pruritus.
the best option for treatment of the metabolic derangements associated with refractory renal HPT
Kidney transplantation
standard surgical options for treatment of renal HPT
- subtotal parathyroidectomy or total parathyroidectomy with autotransplantation.
- transcervical thymectomy to remove potential supernumerary glands, which are most often found in the thymus
When performing a subtotal parathyroidectomy
> > in-situ, 40- to 80- mg well-vascularized, parathyroid remnant is fashioned initially
> > followed by removal of all remaining parathyroid glands after confirming the viability of the remnant.
total parathyroidectomy and autotransplantation
> > the autotransplant is preferably performed in the brachioradialis muscle of the nondominant forearm.
> > This may help avoid reoperation in the neck
allows for differential measurement of PTH in the graft-bearing and non–graft-bearing forearms to help differentiate the remnant from the neck as the site for recurrence
Subtotal vs total ans transplant ?
> > higher rates of recurrence for subtotal parathyroidectomy versus higher rates of hypoparathyroidism for total parathyroidectomy and autotransplantation
Tertiary Hyperparathyroidism
autonomous overproduction of PTH with the development of hypercalcemia in patients with chronic renal failure and preexisting secondary HPT.
Tertiary HPT is also used to define HPT that persists or occurs after successful renal transplantation.
even after transplant ?
up to 25% of patients with secondary HPT will have persistent HPT (tertiary HPT) 1 year after transplantation in the form of diffuse and nodular hyperplasia
PTH effect on kidney transplant
Prolonged PTH increase in kidney transplant recipients is associated with increases risk of bone loss, decreased allograft survival, and decreased patient survival
two treatment options for tertiary HPT
medical therapy with cinacalcet and parathyroidectomy.
Surgery has been shown to be superior to cinacalcet in normalizing calcium and PTH levels at 1 year after surgery as well as lower rates of allograft failure
Indications for parathyroidectomy in tertiary HPT include
-persistent hypercalcemia or hypercalciuria
-renal phosphorous wasting
-low bone mineral density
-nephrocalcinosis
-symptomatic disease
-enlarged parathyroids on imaging.
In patients who are allograft candidates and have tertiary HPT with high PTH and calcium levels
» pretransplant parathyroidectomy should be considered, as it has been associated with improved graft function.
What to expect after the parathyroidectomy in renal HPT
> > Profound postoperative hypocalcemia is common after parathyroidectomy for renal HPT.
> > Postoperative hypocalcemia is attributed to renal osteodystrophy and “hungry bone syndrome” and occurs due to the sudden decline in PTH
surge in bone uptake of calcium as a result of remineralization
how to Tx this hypocalcemia ?
- admission for 3 to 5 days
» oral and intravenous calcium replacement and calcitriol administration.
» Correction of associated hypomagnesemia
calcitriol may take up to 48 hours to work
> > Preoperative calcitriol treatment starting 5 days prior to surgery resulted in a reduction in intravenous calcium requirement postoperatively and a 50% reduction in the length of hospital stay
Calciphylaxis ( calcific uremic arteriolopathy )
> > painful violaceous skin lesions with associated ulceration, ischemia, necrosis, and eschar formation
> > microvascular calcification, intimal proliferation, fibrosis, and thrombotic occlusion of small subcutaneous vessels.
> > affect :
end-stage renal disease
secondary HPT
renal transplant recipients
rarely primary HPT
Calciphlaxis
- Mortality rates of 50% to 80% are reported in patients with calciphylaxis.
- skin biopsy demonstrating vascular and extravascular calcifications in the absence of histologic findings of vasculitis
Tx
Treatment options
-sodium thiosulfate
-phosphate binders
-low calcium dialysate bath
-bisphosphonates
-calcimimetics
-parathyroidectomy.
> > total parathyroidectomy with transcervical thymectomy is the preferred operation
debridement of dry eschar should be avoided since this can lead to progression of calciphylaxis
pathogenesis of calciphylaxis
-medically-refractory hyperphosphatemia
-high calcium-phosphate product
-high PTH levels
-use of warfarin
-protein C and protein S deficiency
-other causes of thrombophilia.
Hyperparathyroidism-Induced Hypercalcemic Crisis
- HPT and advanced malignancy are the two most common causes
- The definition of HIHC :
» an albumin-corrected serum calcium level of 14 mg/dL or greater with associated organ dysfunction - symptoms related to dysfunction of the gastrointestinal, renal, cardiac, and central nervous systems
- Acute pancreatitis is more common in patients with HIHC than in patients with HPT without crisis.
- more likely to have a palpable neck mass than patients with HPT without HC.
- volume depletion, hypokalemia, and acute kidney injury
