Parathyroid and other Ca Disorders Flashcards
Primary function of PTH
Maintain extracellular fluid (ECF) calcium
Important determinant of PTH secretion
Ionized calcium
Direct effects of PTH
BONE: inc bone remodeling
(inc osteoclast-mediated bone resorption, stimulates bone formation)
KIDNEYS: reduce clearance of calcium
(inhibit phosphate reabsorption: prox tubule; promote ca reabsorption: distal tubule; stimulates 1, 25 OH2D which promotes vit D synthesis)
Indirect effects of PTH
INTESTINE: inc efficiency of ca absorption (vit d mediated)
PTH elevation effects
Hypercalcemia*
Hypophosphatemia
Etiologies of primary hyperparathyroidism
Solitary Adenomas: MC
MEN
MEN1 (Wermer’s syndrome)
Parathyroid hyperplasia/adenoma
Pituitary tumors/hyperplasia
Pancreatic tumors/hyperplasia
*Gastric hypersecretion and PUD (ZES)
MEN 2A (Stipple syndrome)
Phaeochromocytoma
Medullary Thyroid Ca
Hyperparathyroidism/adenoma
MEN 2B
Mucosal and/or GI neuromas
Marfanoid features
Medullary thyroid ca
Phaeochromocytoma
Increased giant multinucleated osteoclasts and replacement of the normal cellular and marrow elements by fibrous tissue, subperiosteal resorption of phalangeal tufts
Osteitis fibrosa cystica
Surgery recommended in asymptomatic hyperparathyroidism
Hypercalcemia above the ULN of normal
Hx of life-threatening hypercalcemia
Nephrolithiasis or renal insufficiency
Hypercalciuria: 24h urinary Ca >400mg
Reduction of bone mass more than 2 standard deviations below normal (osteoporosis)
Responsible humoral agent in most cases of malignancy-related hypercalcemia
PTHrP
Two main mechanisms of hypercalcemia in malignancies
Solid tumors associated with hypercalcemia secrete factors that increase bone resorption
Humoral hypercalcemia of malignancy: MC, secretion of PTHrP factor by tumors
Tumors most frequently associated with hypercalcemia
Squamous cell tumors: Lung Kidney Breast Head and neck GU tract
