Parathyroid disorders (Andrews and Washington)

Question 1

The Parathyroid is regulated by

Answer 1

Blood Serum levels of Ca+. (not a pituitary or hypothalamic trophic hormone) Low levels of calcium will increase the release of PTH.

Question 2

3 ways in which the PTH regulates Calcium homeostasis

Answer 2

Bone - reabsorption of Ca+ (osteoclasts mobilized)
Kidney - reabsorption of Ca+ (Renal tubular absorption)
- Vitamin D converted to active 1.25 dihydroxy
- Increased Urinary phosphate excretion
GI - Calcium absorption

Question 3

What is hyperparathyroidism?

Answer 3

Too much Ca+ and PTH in the blood. More common in women than in men.

Question 4

3 causes of Primary hyperparathyroidism

Answer 4

Adenoma - (of one gland) Well circumscribed, soft and tan module. Unaffected glands are normal or small. Few mitosis.
Hyperplasia - Variable enlargement of all parathyroids (hard to find). Chief cell most common
Carcinoma - Hard to distinguish from Adenoma. Usually only diagnosed after metastis

Question 5

Other organs that are affected by hyperparathyroidism (or hypercalcemia)

Answer 5

Skeletal - osteoporosis (weakened bones)
Kidneys - Nephrolithiasis (kidney stones) and Nephrocalcinosis (granulation)
Metastic calcification - GI, lungs, myocardium, blood vessels

Question 6

Other signs and symptoms of hyperparathyroidism (or hypercalcemia)

Answer 6

GI - (slows it down, nausea, constipation, peptic ulcer, pancreatitis, gallstones)
CNS - Motor and cognitive depression, seizures
Neuromuscular - Weakness and Hypotonia (low muscle tone)

Question 7

What is Secondary hyperparathyroidism.

Answer 7

Chronic hypocalcemia (usually due to chronic renal failure). Can also be caused by due to inadequate dietary calcium and Vitamin D. deficiency. . Morphology mimics primary hyperplasia

Question 8

Most common cause of hypoparathyrodism is

Answer 8

Iatrogenic (due to thyroid removal)

Question 9

Causes of Hyperparathyroidism

Answer 9

1) Surgical removal of thyroid
2) Autoimmune destruction of gland (by itself of associated by other endocrine a/I disorders
3) Thymus aplasia - T-cells (close to thymus)

Question 10

S/s of Hyperparathyroidism

Answer 10

Tingling, Nueromuscular irritability, Chvostek’s sign (tap side of jaw and muscle will move) and Trousseau’s sign (flexing of the wrist and metacarpal joints), Seizures, Cataracts, Dental abnormalities, osteosclerosis (elevated bone density)

Question 11

Low calcium and Intact PTH means

Answer 11

Hypoparathyroidism

Question 12

Low calcium and high Intact PTH means

Answer 12

Renal failure

Question 13

High calcium and intact PTH means

Answer 13

Primary hyperparathyroidism

Question 14

High calcium and low intact PTH means

Answer 14

Hypercalcemia of malignancy.

Question 15

4 components of Calcium homeostasis

Answer 15

1) Serum Calcium
2) Serum Phosphate
3) 1,25-dihyroxyvitamin D-3
4) PTH

Question 16

Calcium distribution in the boday

Answer 16

99% stored in bone.
.5% in plasma bound to plasma proteins
.4% free or ionized (most important for physiologic function)

Question 17

Primary functions of Calcium

Answer 17

1) Provide electrical energy to our nervous and muscular systems (nerve and muscle conduction)
2) Provide strength to skeletal system
3) Enzymatic function in blood clotting
4) Required for hormone secretion
5) Plasma membrane stability and permeability.

Question 18

PTH action on the kidneys

Answer 18

Increases renal calcium reabsorption in the tubules (keeps it from being excreted in urine)
Increases phosphate excretion by blocking reabsorption
Increases the conversion of Vitamin D to its active form in the kidneys which increases GI absorption of Ca+. Vitamin D is needed to absorb Ca+

Question 19

PTH action on bones. Two phases

Answer 19

Rapid (within minutes) binds to receptors on osteoblasts (make bone) and osteoclasts (break down bone) and transports Ca+ to blood stream
Slow (days) - Osteoclasts are activated and breakdown formed bone with results in an increase in osteoclastic activity releasing to blood.

Question 20

Vitamin D (formed by) use

Answer 20

Vitamin D3 is formed in skin and UV (D2 from diet). Its activated when it undergoes 25-hydroxylation ni the liver . 1-hydroxylation in kidneys is bioactive form
It that form it promotes intestinal absorption of calcium and enhances bone absorption of Ca

Question 21

As Ca+ levels go up…

Answer 21

PTH secretion goies down. Renal vitamin D activation goes down, intestinal Ca+ absorption goes down and there is a rise in renal phosphate reabsorption

Question 22

What phosphate is/does

Answer 22

85% in bone. It acts as a intra cellular and extracellular anion buffer for acid base balance and provides energy for muscle contraction in ATP form.

Question 23

Calcitonin, what it is, what it does

Answer 23

Produced by thyroid. Deacreases ECF Ca+ levels (to a much lesser degree than PTH and Vitamin D). In the bones it inhibits Ca+ reabsorption by inhibiting osteoclasts and in the kidneys it stimulates Ca+ and phosphate excretion in renal tubules