U1 day 10 - metabolism

Question 1

Biological action of thyroid hormone

Answer 1

Two main effects: metabolism/ regulation of basal metabolic rate, and cell growth and differentiation

Question 2

T3 general stuff

Answer 2

Active form of thyroid hormone, singles via activation of nuclear receptors and changes in gene expression, needs to cross the plasma membrane via MCT8, receptor is TR

Question 3

TRβ: chromosome 3

Answer 3

Isoform β1 and β2 bind to T3, β2 is limited to the pituitary and CNS, β1 is precent in numerous tissues.

Question 4

TRα: chromosome 17

Answer 4

Isoform 1, binds to T3. α1 is present in numerous tissues

Question 5

TR exceptions

Answer 5

With absence of ligand, TR association with nuclear chromatin. Can heterodimer with the retinoid X receptor. In absence of ligand TR-RXR represses gene expression.

Question 6

TR independent signaling

Answer 6

T3 can induce cellular changes very rapidly by nuclear independent signaling, not totally sure how it works, causes uptake in amino acid, glucose, and oxygen consumption.

Question 7

Basal metabolic rate

Answer 7

energy expanded to maintain basic function under thermal neutral conditions, proportional to body volume and oxygen consumption, can change based on thyroid hormone status.

Question 8

T3 affect on BMR

Answer 8

↑ BMR,
Tissue: heart, liver, muscle, GI, and kidney.
Target: Na+/K+ and ATPase
Signal interactions: Sympathetic nervous system (SNS)

Question 9

T3 affect on adaptive thermogenesis

Answer 9

↑ adaptive thermogenesis
Tissues: Brown adipose tissue, and white adipose tissue
Target: UCP1 (burns fat), D2 (activates T4 to T3)
Signal interactions: SNS, bile acids

Question 10

T3 affect on gluconeogenesis

Answer 10

↑ gluconeogenesis
tissues: liver and muscles
Target: PEPCK (phosphoenolpyruvate carboxykinase)
signaling interactions: glucose and insulin

Question 11

T3 affects on insulin secretion

Answer 11

Decrease in sensitivity
Tissues: Pancreas
Target: GLUT4 (glucose transporter)
Signaling interactions: STEBP (sterol response element-binding protein) LXR (liver X receptor)

Question 12

T3 and neurodevelopment

Answer 12

T3 is necessary for the development of many tissues and organs but especially the nervous system, particularly in fetal development of CNS.

Question 13

Negative feedback loop of TSH

Answer 13

Thyrotroph have high levels of D2; turns T4 into T3. T3 binding to its nuclear receptor TRβ2 inhibits synthesis of B subunit, (inhibits release of TSH) T3 also decreases thyrotroph TRH receptor expression, T4 inhibit secretion of TSH.

Question 14

Autoregulation of T4 and T4

Answer 14

dependent on how much Iodine, Tg iodination can be blocked, this is used in wolff-chaikoff effect in medicine.

Question 15

Hypo and Hyperthyroidism present with what

Answer 15

enlarged thyroid gland, and overstimulation of TSH receptor

Question 16

hyperthyroid disterbances

Answer 16

tachycardia, increase in appetite, increase of intestinal peristalsis, decrease in weight, weakness and deterioration of skeletal muscles, Hyperactive nervous system, warm and moist skin, increase in BMR

Question 17

hypothyroid disterbances

Answer 17

decrease in HR, Decrease in appetite, decrease in intestinal peristalsis, increase in weight, slow and stiff muscles, hypoactive nervous system, memory loss, cool dry skin, decrease in BMR

Question 18

Graves’s disease (GD)

Answer 18

Thyrotoxicosis: excess thyroid hormone
polygenetic disorder, autoimmune disease, more common in women, 50-80% of hyperthyroidism cases, continuous TSH stimulation.

Question 19

Hashimoto’s disease

Answer 19

most common hypothyroidism in developed countries, autoimmune disease, destruction of follicles, low circulation of T3 and T4, increased TSH release, enlarged thyroid gland