Parathyroid Flashcards
(21 cards)
What is the primary stimulator of PTH release?
-low free serum Ca
What are the 4 physiologic actions of PTH?
- bone resorption (Ca+phosphate)
- Ca REABSORPTION in the DCT
- phosphate EXCRETION in PCT
- adding 1-OH to activate Vitamin D
What type of bone cell does PTH stimulate?
osteoClasts
What enzyme in the PCT of kidney is stimulated by PTH?
- 1a-hydroxylase
- adds an -OH @ position 1 to 25-OH Vitamin D
When is the only time that Calcitonin plays a role in the body?
-if Ca levels are super hi, it will reduce osteoClast activity
What 3 diseases can benefit from Calcitonin administration?
- Osteoporosis
- Paget’s disease of bone
- malignancies with hyperCa
PTH is to Chief cells of the parathyroid as Calcitonin is to __________
-C cells of the THYROID
What the hell is parathyroid related peptide (PTHrP)?
- secreted by many cancerous tissues
- causes hyperCa
Why do patients with renal failure have bone problems?
-less active Vitamin D, become hypoCalcemic
Patients with renal failure will have high levels of what in the blood?
- hi PTH
- hi 25-OH Vitamin D (inactive)
- hi phosphate
Vitamin D acts where and does what?
- intestine
- increases absorption of BOTH Vitamin D +Phosphate
What 2 ions inhibit ADH at the collecting duct and cause polyurea?
- HypoKalemia
- HyperCalcemia
Describe a patient with primary hyperPTH.
- most are asymptomatic!
- BONES (osteoporosis)
- STONES (nephrolithiasis)
- GROANS (constipation)
If a pt with primary hyperPTH is asymptomatic, what tx?
NONE
What does hypoCalcemia do to your nerves?
HYPERexcitable (+Chvostek’s sign on face, +Trousseau sign with bp cuff on arm)
Primary hyperparathyroidism presents commonly as what triad?
-Stones, bones, and groans
Ca-oxolate kidney stones, cystic bone spaces, constipation
What 4 lab values to look for in a Parathyroid adenoma?
- hyperCa
- hypoPhosphatemia
- hi alk phos
- hi urinary cAMP (say whaaaa)
What are Chief Cells?
- cells of parathyroid
- secrete PTH
What are parafollicular (C) cells?
- cells near the follicles in the thyroid
- secrete Calcitonin
- cancer=medullary carcinoma of thyroid (MEN II)
What is the number 1 cause of secondary hyperparathyroidism?
-Chronic renal failure
Describe the 2 mechanisms by which renal failure leads to secondary hyperparathyroidism.
- renal failure = less excretion of Pi (more Pi=more gobbling up of free Ca)
- renal failure = less 1-OH added to Vitamin D (no active Vit D = less Ca absorption in gut)
- less free Ca = more PTH
