Parathyroid Disease Flashcards
What are the two major anatomical variations that can occur with the inferior parathyroid glands?
May sometimes follow the thymus and end up in the superior mediastinum
5th PT gland development
What is the chromosome that has the PTH gene?
Chromosome 11
What is the half life of PTH?
2-4 minutes
What two organs clear PTH?
Liver and kidney
What is significance of the breakdown products of PTH?
Fragments are thought to have their own receptors and biological activity
What are the modern iPTH assays useful for?
Assaying for the intact PTH
True or false: modern iPTH assays are able to detect both high and low levels of iPTH
True
Where are CaR receptors found?
Ubiquitous
What, besides [Ca] cause secretion of PTH? (3)
Mg
Vit D
Catecholamines
What is the effect of PTH on the proximal tubule? Distal?
Proximal = Decreases phosphate reabsorption
Distal = increases Ca reuptake
Where is most of the Ca in the renal tubules reabsorbed? What is the role of PTH in this?
Most reabsorbed in the proximal tubule, which is NOT affected by PTH
Where does PTH act in the kidney (proximal or distal tubule)?
Distal
Most Ca reabsorption in the kidney occurs where? Is this regulated? What about the fine tuning of Ca? What is this usually brought in with?
Proximal tubule where most occurs (and is not regulated), but fine tuning in the distal nephron
H2CO3 + Na
What is the effect of PTH in the proximal tubule of the kidney in terms of phosphate reabsorption?
Inhibits phosphate
What type of metabolic disturbance (acidosis/alkalosis) can occur with abnormally elevated PTH levels?
Hyperchloremic metabolic acidosis
What are the three main causes of decreased PTH hormone?
- Hypoparathyroidism
- Hypercalcemia of malignancy
- Hypomagnesemia
What is the most common cause of increased PTH levels in ambulatory patients?
Hyperparathyroidism
What is the most common cause of increased PTH levels in hospitalized patients?
Malignancy
What is the first line test for a hypercalcemic patient?
PTH levels
What are the components of the VITAMINS TRAP mnemonic for hypercalcemia (just vitamins bit)?
- Vits A and D xs
- Immobilization
- Thyrotoxicosis
- Addison’s ds
- Milk-alkali/metastatic ds
- Inflammatory ds
- Sarcoid
What are the components of the VITAMINS TRAP mnemonic for hypercalcemia (just TRAP bit)?
- Thiazides
- Rhabdo
- AIDS
- Paget’s ds
What type of diuretics may cause hypercalcemia?
Thiazide diuretics
Which gender more commonly gets primary hyperPTH? What is the most common cause of this?
Female
Single PTH adenoma
What genetic disease may lead to primary parathyroid adenomas?
MEN2A/2B
What happens to [Ca] with primary hyperPTH? [Phosphate]? [iPTH]? Urine [Ca]?
- Increased serum [Ca]
- Decreased or = serum [phosphate]
- Increased PTH
- Increased urine Ca
What are the classical x-ray findings of hyperparathyroidism (hands, skull)?
Loss of cortical bones (wrists much greater than hip/spine on DXA scan)
Salt and pepper skull
What is the cure for primary hyperPTH?
Surgical
True or false: it is necessary to look at ALL parathyroid glands if there is hyperPTH
True
What is the treatment for PT hyperplasia?
Subtotal parathyroidectomy, leaving 50 mg of PT tissue in situ OR in forearm
What is Hungry bone syndrome?
In pts treated for severe PTH bone disease, the bones mop up Ca as the parathyroid drive ceases
How do you monitor for a loss of a parathyroid gland during surgery? What should this show if you excised the right gland?
Intraoperative PTH
More than 50% drop
What is the medical therapy for primary hyperPTH? (3)
- Avoid diuretics
- Hydrate
- Calcimimetics
Why is estrogen not used for treating hyperPTH?
Side effects
What is the role of bisphosphonates in the medical therapy of hyperPTH?
Decrease bone turnover
How often should you monitor pts with primary PTH pts undergoing medical therapy? What should be measured?
6 months
-Serum [Ca], DXA scans
What are the two major secondary causes of hyperPTHism?
- Vit D deficiency
- Renal failure
What is familial hypocalciuric hypercalcemia?
Inactivating mutation in Ca sensor/receptor in the kidney/parathyroids, leading to mild hypercalcemia and normal to elevated iPTH
What is the treatment for asymptomatic familial hypocalciuric hypercalcemia?
nothing
How do you differentiate familial hypocalciuric hypercalcemia from hyperparathyroidism?
Familial will have normal urine Ca levels
What are the two general causes of hypoPTH?
Decrease production or response
What are the causes of hypoPTH?
- Surgical complications
- Infiltrative ds
- Autoimmune destruction
What is the autoimmune ds that can lead to hypoPTH?
AI Polyglandular syndrome type 1
What congenital syndrome may cause hypoPTHism?
DiGeorge syndrome
What metabolic disturbance can cause hypoparathyroidism?
Hypomagnesemia
What do the ssx of hypoparathyroidism depend on?
Degree and rapidity of onset of hypocalcemia
What are the acute ssx of hypoparathyroidism? Chronic?
- Acute = Paresthesias, Tetany
- Chronic = Apathy/depression
What are the brain CT findings with hypoparathyroidism?
Calcification of basal ganglia and benign intracranial HTN
What are the GI ssx of hypoparathyroidism?
Nausea/vomiting/ abdo pain
What are the EKG findings of hypocalcemia?
Prolonged QT
What are the eye effects of hypoparathyroidism?
Cataracts
What other diseases can mimic hypoparathyroidism
- Vit D resistance
- Malabsorption
- Decrease Ca mobilization from bone 2/2 metastatic ds
What GI organ complication can cause hypocalcemia?
pancreatitis
What hematological disturbance can cause a hypocalcemia?
albumin
What other ion should be measured with hypocalcemia?
Mg
A decrease in 25 vit D3 indicates what organ pathology?
Liver
A decrease in 1, 25 vit D3 indicates what organ pathology?
Kidney
How do you correct Ca levels with low albumin?
Nl [Alb] - pts [alb]x0.8 + [Ca]
What is the treatment for hypocalcemia?
- IV Ca gluconate
- Vit D3
Who should be treated for hypocalcemia?
If symptomatic or has complications
What is the new drug for treating hypocalcemia? How is this administered?
NATPARA (synthetic PTH analog)
SQ QD
What is the role of NATPARA in treating hypocalcemia?
Reduces the dose of Vit D and Ca needed
True or false: NATPARA decreases the risk of renal calculi
True
What is pseudohypoparathyroidism types 1A and 1B?
End organ resistance to PTH d/t defects in the Gs subunits
What are the lab findings of pseudohypoparathyroidism types 1A and 1B? (Ca, phosphate, PTH)
- Hypocalcemia
- Hyperphosphatemia
- High iPTH
What is Albright’s hereditary osteodystrophy pseudohypoparathyroidism type 1 A? SSx?
Type 1 pseudohypoparathyroidism that causes:
- short stature
- short metacarpals
- Calcified basal ganglia
- mild mental subnormality
What are the characteristic hand findings of Albright’s hereditary osteodystrophy?
- Dimples over the MCPs
- Brachydactyly of the hand
- Short, wide thumb
What is the difference between pseudohypoparathyroidism types 1A and 1B?
Same, but no physical findings with 1b
What is pseudo-pseudohypoparathyroidism?
Same phenotype of pseudohypoparathyroidism type 1A, but NO biochemical abnormalities
What causes the super high PTH levels in pseudohypoparathyroidism?
Resistance to PTH, NOT deficiency
Salt and pepper skull is seen in what disease?
Primary hyperparathyroidism
What is the treatment for parathyroid hyperplasia?
Remove 3.5 glands
True or false: if a patient is symptomatic from primary hyperparathyroidism, you have to do surgery
True
What is the CrCl level that indicated the need for surgery with primary hyperparathyroidism? What other renal symptom indicates the need for surgery?
Less than 70%, OR have a h/o stone
What is the serum [Ca] level that indicated the need for surgery with primary hyperparathyroidism?
More than 1 mg/dL above the normal limits
What is the bone mineral density T score that indicated the need for surgery with primary hyperparathyroidism? What bone(s) must this be?
Less than 2.5 SD at ANY site
What is the age that indicated the need for surgery with primary hyperparathyroidism?
Less than 50 y.o.
What is tertiary hyperparathyroidism?
Continuous parathyroid stimulation in secondary leads to an autonomous parathyroid gland
