EXAM #1: PARATHYROID DISEASES Flashcards
What is the embryologic origin of the parathyroid glands?
Superior= 4th pouch Inferior= 3rd pouch
What is a common location of ectopic parathyroid gland?
Superior mediastinum
What are the two major types of cells in the parathyroid gland?
1) Chief cells
2) Oxyphil cells
What chromosome is the gene that is responsible for PTH located on?
Chromosome 11
How should you order PTH levels?
iPTH–intact PTH
*Note that the breakdown products also have biologic activity
What controls PTH secretion?
Ca++
- Mg++
- Vitamin D
- Catecholamines
*Low Ca++ leads to PTH secretion
What are the three target organs for PTH?
1) Bone
2) Intestinal mucosa
3) Kidney
What is the effect of PTH on bone?
Increased osteoclast activity causing resorption (release into circulation) of Ca++ and phosphate
What is the effect of PTH on the kidney?
- Retain Ca++
- Excretion of phosphate
What is the effect of PTH on the gut?
Increased gut absorption of Ca++
What is the NET effect of elevated PTH?
1) Increased serum Ca++
2) Decreased serum phosphate
Where does Ca++ absorption occur in the kidney?
Proximal tubule
Where does PTH fine-tune Ca++ in the kidney?
DISTAL nephron
What is the effect of PTH on bicarbonate?
Impaired reabsorption of HCO3-
What is the acid/base effect of elevated PTH?
Hyperchloremic metabolic acidosis
What is the first line test in a hypercalcemic patient?
PTH level
What is the most common cause of hypercalcemia in ambulatory patients? What about hospitalized patients?
Ambulatory= Hyperparathyroidism
Hospitalized= malignancy
What is the most common cause of primary hyperparathyroidism?
Single parathyroid adenoma
What is the mnemonic to remember the major clinical features of primary hyperPTH?
- Bones= long bone pain
- Stones= kidney stones
- Groans= gastric ulcers
- Moans= psychiatric sx. -depression
What are the expected labs for hyperPTH?
- Increased Ca++ (chronic)
- Decreased phosphate
- Increased or normal iPTH*
- Increased urine Ca++
Generally, how does hyperPTH effect bone?
Decreased bone density, especially in cortical bone
What bone must be checked for a DEXA scan with likely hyperPTH?
Wrist
Hip/spine is different type of bone that is not usually as implicated in the osteoporosis caused by hyperPTH
What is the definitive treatment for primary hyperPTH?
Surgery
What are the indications for surgery in primary hyperPTH?
1) Symptoms
2) Serum Ca++ greater than 1 over upper normal limit
3) Creatinine clearance less than 70%
4) Less than 50 y/o
What are the complications of surgery in primary hyperPTH?
1) Recurrent laryngeal nerve damage
2) Hypocalcemia
3) Hungry bone syndrome
What is hungry bone syndrome?
- Severe disease drastically drives Ca++ OUT of bones
- That drive is removed
- Bones react by “mopping up” Ca++ as PTH drive stops
*Results in severe acute cases of hypocalcemia
What are the medical therapies for primary hyperPTH?
1) Avoid dehydration
- No diuretics
- H20
2) Bisphosphonates (decrease bone turnover)
3) Calcimimetics
4) Monitoring with Ca++, creatinine, DEXA
What are the most common causes of secondary hyperPTH?
1) Vitamin D deficiency
2) Renal failure
What causes tertiary hyperparathyroidism?
Renal failure
*This is when there are renal failure leads to autonomously functioning parathyroid glands
What is FHH?
Familial Hypocalciuric Hypercalcemia
What is Familial Hypocalciuric Hypercalcemia?
- Inactivating mutation of Ca++ receptor
- Mild hypercalcemia/ iPTH
- Low urinary Ca++
Is treatment indicated for FHH?
NO
What are the basic causes of hypoPTH?
1) Low PTH production
2) Resistance to PTH (receptor level problem)
What is the most common cause of hypoPTH?
Surgical excision
What are the symptoms of hypoPTH dependent on?
The DEGREE and RAPIDITY of hypocalcemia
What are the major sx. associated with hypoPTH?
asdf
Pathoma
What are the net physiologic effects of hypoPTH?
- Decreased Ca++
- Increased phosphate
What cancer is associated with hypocalcemia?
Prostate cancer i.e. an “osteoblastic metastasis”
What do you need to correct a serum Ca++ for?
Serum albumin
- Albumin greater than 4= lower Ca++
- Albumin less than 4= higher Ca++
How should you approach hypocalcemia?
1) Measure iPTH
2) Measure Vitamin D
3) Measure Mg++
How is hypocalcemia treated?
1) IV or PO calcium
2) Vitamin D
AND
3) Synthetic PTH analog (NATPARA)
*Note expensive and subQ; good for non-compliant patients
What are the two types of pseudo pseudohypoPTH?
Types 1A and 1B
*Both are problems with end-organ resistance to PTH
What are the labs associated with Type 1A and 1B pseudohypoPTH?
1) Low Ca++
2) High Phosphate
3) High iPTH
What is the major difference between pseudohypoPTH 1A and 1B?
No physical manifestations
What is pseudo pseudohypoparathyroidism?
Physical manifestations without lab abnormalities
