Modules (Week 2)

Question 1

What cells in the Parathyroids synthesize, store and secrete PTH

Answer 1

Chief cells

Question 2

Main functions of PTH are to (increase/decrease) Calcium and (increase/decrease) phosphorus

Answer 2

Inc. Calcium

Dec. Phosphorus

Question 3

Where does PTH act?

Answer 3

1. Bone-direct effect (inc. bone resorption to inc. Ca and Phosphorus release)
2. Kidney-direct effect (inc. Ca reabsorption and Phosphorus excretion; inc. Vit D activation)
3. Gut-indirect effect (inc. Ca and Phosphorus absorption via Vit D activation)

Question 4

Function of PTH on bone

Answer 4

Direct effect on bone:

• Inc. bone resorption
• Inc. Ca and Phosphorus release

Question 5

Function of PTH on Kidney

Answer 5

Direct effect on kidneys:

• Inc. Ca reabsorption
• Inc. Phosphorus EXCRETION
• Activate Vitamin D

Question 6

Function of PTH on Gut

Answer 6

INDIRECTLY inc. Ca and Phosphorus absorption via Vitamin D

Question 7

(Calcium/Phosphorus) is the MAIN regulator of PTH via a Negative feedback loop

Answer 7

Calcium (too little, need to conserve and retain)

Question 8

(Calcium/Phosphorus) is a regulator of PTH via a Positive feedback loop

Answer 8

Phosphorus (too much, need to excrete)

Question 9

Calcium binds to ______________ _________________ ________________ on Chief cells to regulate PTH

Answer 9

Calcium-Sensing Receptor (CaSR)

Question 10

What is the Diagnostic Approach for a potential Parathyroid issue?

Answer 10

1) High/Low/Normal calcium?

2) If normal calcium, is there abnormal PTH or Vitamin D?

Question 11

How is Calcium regulated/stored in ECF

Answer 11

Protein bound (~40%)
Ionized (free/bioactive) (~50%)
Complexed (with anion like PO4, HCO3, lactate) (~10%)

Question 12

(Low/High) albumin is the most common cause of apparent hypocalcemia or “pseudohypocalcemia”

Answer 12

Low albumin (due to overall lower measured TOTAL calcium without a true change in overall body calcium)

Ionized (free) calcium does not change! (so no symptoms of hypocalcemia)

Question 13

Free calcium (increases/decreases) with alkalemia

Answer 13

Decreases (protein-bound Ca increases)

• symptoms of hypocalcemia can occur!
• but TOTAL calcium does NOT change!

Question 14

Free calcium (increases/decreases) with acidemia

Answer 14

Increases (protein-bound Ca decreases)

*but TOTAL calcium does NOT change!

Question 15

Function of Phosphorus

Answer 15

Bone structure

ATP generation

Question 16

Hormones that regulate Phosphorus levels

Answer 16

decreased by PTH (renal excretion)

increased by Vit. D (gut absorption)

Question 17

Renal failure, Hypoparathyroidism and Vit. D toxicity result in (low/high) Phosphorus

Answer 17

High Phosphorus (lots of gut absorption, little renal excretion)

Question 18

Hyperparathyroidism and Vit. D deficiency result in (low/high) Phosphorus

Answer 18

Low (little gut absorption, lots of renal excretion)

Question 19

Function of Magnesium

Answer 19

Catalyze actions of cellular enzymes (utilizing or synthesizing ATP)

Question 20

SEVERE (Hyper/Hypo)magnesemia can blunt PTH release

Answer 20

Hypomagnesemia

Question 21

Chronic Kidney Disease (elevated creatinine) can result in (high/low) levels of PTH

Answer 21

High PTH (to stimulate kidneys b/c of decreased serum calcium & increased serum phosphorus due to kidney disease)

Question 22

The activation of Vitamin D from Cholecalciferol (skin) or Ergosterol (supplement) requires….

Answer 22

2 hydroxylation steps

• one in liver by 25-hydroxylase
• one in kidney by 1 a-hydroxylase

Question 23

Pro-hormone and storage form for Vitamin D

• indicator of vitamin D status

Answer 23

25-OH-D3 (cholecalciferol) OR 25-OH-D2 (ergosterol)

• this occurs in the liver by 25-hydroxylase

Question 24

Chemical formula for Vitamin D and biologically active form

• indicator of calcium disorders

Answer 24

1,25-OH2-D3 (cholecalciferol) OR 1,25-OH2-D2 (ergosterol)

• this occurs in the kidney by 1 a-hydroxylase
• this step is stimulated by PTH

Question 25

What can cause low Vitamin D levels (storage vs. bioactive forms)

Answer 25

Storage Form: - Dec. sun exposure - Dec. Vitamin D intake - Malabsorption - Liver disease Bioactive Form: - Dec. kidney function - Dec. PTH

Question 26

How is Parathyroid Hormone-Related peptide different from PTH

Answer 26

Same effect on bone and kidney, BUT less likely to stimulate bioactive form of Vitamin D (1, 25-OH-D) so less effect (although indirect) on intestine

Question 27

Function of Parathyroid Hormone-Related Peptide

Answer 27

1. Same effect on bone and kidney as PTH. 2. Teeth eruption, mammary gland development and lactation 3. PTH-RP is increased in humoral hypercalcemia of MALIGNANCY

Question 28

Cells that secrete Calcitonin

Answer 28

C-Cells (Parafollicular cells of Thyroid)

Question 29

Roles of Calcitonin

Answer 29

OPPOSITE of PTH at bone, kidney, and gut - Overall: lower serum Calcium * Can be used as a marker for monitoring medullary thyroid cancer recurrence

Question 30

Iodine is transported into the thyroid cells via what transporter?

Answer 30

Na/I- symporter

Question 31

What enzyme catalyzes the reaction of Thyroglobulin and Iodine to T3/T4

Answer 31

Thyroid Peroxidase

Question 32

(T3/T4) has a very short half-life, around 1 day

Answer 32

T3

Question 33

(T3/T4) is the vast majority of thyroid hormone secreted

Answer 33

T4 *is pro-hormone and must be converted to T3

Question 34

(T3/T4) is the pro-hormone and must be activated into the biologically active form

Answer 34

T4

Question 35

(T3/T4) is the biologically active form

Answer 35

T3

Question 36

What are the "4 B's" of Thyroid hormone action

Answer 36

Brain maturation Bone growth Beta-adrenergic effects (cardiac) Base metabolic rate

Question 37

What labs do you want to run to assess Thyroid function?

Answer 37

``` TSH TBG-T3 and T4 Free T3 and T4 Thyroid antibodies Thyroid tumor markers ```

Question 38

Functions of TSH (Thyroid Stimulating Hormone)

Answer 38

Stimulate thyroid hormone synth/release | Growth and vascularity of thyroid

Question 39

The majority of T3/T4 is bound to..

Answer 39

Thyroxine Binding Globulin (TBG)

Question 40

What can caused an Increase in Thyroid Hormone Binding proteins

Answer 40

ESTROGEN | Pregnancy

Question 41

What can cause a Decrease in Thyroid Hormone Binding proteins

Answer 41

ANDROGENS Glucocorticoids Chronic Liver Disease

Question 42

Why is measuring TSH the BEST test to diagnose and follow primary disorders in Thyroid Function?

Answer 42

Reflects long-term feedback of T3/T4 on pituitary in the recent past *also have opposite, logarithmic change in TSH vs. T3/T4

Question 43

Antibodies seen in Autoimmune Thyroid Disease (2 total)

Answer 43

Thyroid Peroxidase antibodies (TPOAb)* TSH-Receptor antibodies (TRAb)* Thyroglobulin Antibodies (TgAb) *best indicators

Question 44

Which antibody is present in 90-95% of Autoimmune Thyroid Disease

Answer 44

Thyroid Peroxidase Antibodies (TPOAb)

Question 45

TSH Receptor Antibodies are inhibitory and decrease the activity of the Thyroid (True or False)

Answer 45

False; can actually be either Stimulating (TSI) or Inhibitory (TBII)

Question 46

What are the Thyroid Tumor markers used for SURVEILLANCE (2 total)

Answer 46

Thyroglobulin (papillary/follicular thyroid cancer) | Calcitonin (MTC)