Parathyroid Flashcards
What is the phys of calcitonin release?
- Parafollicular cells (C-cells) of thyroid gland secrete calcitonin in response to high Ca levels, this counteracts effects of PTH
What is the phys of PTH release?
- PTH secreted by chief cells of parathyroid gland
A. Parathyroid cells sense low serum Ca - PTH released → ↑ renal absorption of Ca → initiates conversion of Vit D to active form → intestinal absorption of dietary Ca → initiate bone resorption
- Decreases renal absorption of phosphorus, lowering serum phosphate level
What is hyperparathyroidism?
1. Excessive secretion of PTH A. ↑ Plasma calcium levels 3. Excessive excretion of phosphorus A. Phosphaturia B. ↓ Plasma phosphate levels
What is hypoparathyroidism?
- Inadequate secretion of PTH
A. ↓ Plasma calcium levels
B. ↑ Plasma phosphate levels
Define primary hyperparathyroidism
- Overproduction of PTH → abnormal calcium homeostasis
- F > M
A. Prevalence 1:1000 in US - Mean age 52-56yo
- ↑ risk w/ age
- ↑ in menopausal women
What is the most common cause of primary hyperparathyroidism?
- Most caused by single parathyroid adenoma
A. Chief Cell Adenomas 85% of all cases
B. Some multiple adenomas
C. Etiology of most adenomas unknown
D. Some familial as part of Multiple Endocrine Neoplastic syndromes (MEN 1 and 2)
What is the pathophys of primary hyperparathyroidism?
- PTH “shut-off” feedback is lost
2. Leads to excessive production of PTH
What are complications from primary hyperparathyroidism?
- Leads to excessive resorption of Ca from bone
A. Osteopenia
B. Osteitis Fibrosa Cystica (OFC) in severe cases
(diffuse demineralization, pathological fractures, and cystic bone lesions) - Leads to renal tubular reabsorption of calcium
A. Predisposes to formation of renal stones
B. ↑ Ca in filtrate results in hypercalciuria
What is the clinical presentation of hyperparathyroidism?
- Most cases discovered incidentally by routine chemistry panel (hypercalcemia)
- Symptoms:“bones, stones, abdominal groans, psychic moans, w/fatigue overtones”
What are the skeletal sxs of hyperparathyroidism?
- Cortical bone loss
- Bone & joint pain
- Pseudogout
A. Chondrocalcinosis- Calcium phosphate deposition
B. Crystal deposits in joints on X-ray
C. Streaking of soft tissue w/ calcium
What are the renal manifestations of hyperparathyroidism?
- Nephrolithiasis
- Polyuria
- Hypercalciuria
- Rare nephrocalcinosis: calcification of kidneys
What are the abdominal sxs of hyperparathyroidism?
- Abd pain
- Anorexia
- N/V -> dehydration
- Constipation
- Peptic ulcers
- Acute pancreatitis
What are the psychologic moans of hyperparathyroidism?
- Subtle
- Depression
- Inability to concentrate
- Memory problems
What are the CNS manifestations of hyperparathyroidism?
- Fatigue overtones
A. Malaise
B. Irritability
C. Insomnia
What are the neuromuscular manifestations of hyperparathyroidism?
- Fatigue overtones
A. Muscle cramps
B. Weakness
C. Paresthesia
What are the cardiac manifestations of hyperparathyroidism?
- fatigue overtones?
A. Hypertension
B. Bradycardia
C. LVH
What are the CMP results in hyperparathyroidism?
- inc Serum Calcium > 10.5 mg/dL
- ↓ Serum Phosphate (PO4)
A. Normal 2.7-4.5 mg/dL
B. > 60 yr M 2.3-3.7 mg/dL
C. > 60 yr F 2.8-4.1 mg/dL - ↑ Alkaline Phosphatase only if bone turnover is present
A. M 38-126 U/L (nl)
B. F 70-230 U/L (nl) - BUN/Cr
- Lipase/Amylase if abd pain
What are the PTH results of hyperparathyroidism?
↑ (or high normal), confirms Dx
What do you do if the pt has ↑ PTH & normal serum calcium?
- Evaluate for 2°hyperparathyroidism (vit D or calcium deficiency, hyperphosphatemia, or renal failure)
- If no secondary cause found:
A. Cont. monitoring
B. ≈ 19% will develop hypercalcemia over next 3 years
What do you do if the pt is positive for hyperparathyroidism?
- Screen for Familial Benign Hypocalciuric Hypercalcemia (FBHH) w/ 24-hour urine for calcium & creatinine
- Calcium excretion of < 50 mg/24 hr atypical for primary hyperparathyroidism & indicates possible FBHH
When are imaging studies used in hyperparathyroidism?
- Not useful in the Dx of hyperparathyroidism
- Parathyroid imaging is crucial in those w/ prior neck surgery
A. MRI preferred - Non-contrast CT scan of kidneys to determine calcium-containing stones
- DEXA scan (bone density scan) to determine bone loss
What is the imaging study of choice for the neck?
MRI
What are the DDX for hyperparathyroidism?
- Lab error, initially should be repeated ALWAYS
- Dehydration
- Malignant tumors (breast, lung, pancreas, uterus)
- Multiple Myeloma, especially in elderly
- Sarcoidosis
- Large consumption of calcium or vit D, especially w/ thiazide diuretics
- Adrenal Insufficiency
- Familial Benign Hypocalciuric Hypercalcemia (FBHH)
- Hyperthyroidism
How are asymptomatic hyperparathyroid pts treated?
- May not need therapy
- Advise to keep active, avoid immobilization, & drink ↑ fluids
- Avoid:
A. Thiazide diuretics
B. Large doses vit. A
C. Calcium-containing antacids - Follow-Up
A. Serum calcium, albumin, BUN/Cr q 6 mo
B. Urine calcium annually
C. DEXA scan q 2 yr