Micronutrients (Bind to Type II Steroid Hormone Receptors)

Question 1

What are cytosolic receptors?

Answer 1

ligand binds to receptor in the cytoplasm, and migrates into the nucleus to impact transcription

Question 2

What are nuclear receptors?

Answer 2

ligand binds to receptor in the nucleus to impact transcription

Question 3

What are the Group 1 micronutrients?

Answer 3

- Bind to Type II Steroid Hormone Receptors
- Iodine, Vit. A, Vit. D (bind to recpeotr)
- Calcium, Vit. K, Phosphorus, Fluoride

Question 4

What’s the role of iodine?

Answer 4

makes T3 hormone to regulate basal medtabloic rate

Question 5

What’s the role of vitamin D?

Answer 5

converted into calcitriol to regulate calcium

Question 6

Whats the role of vitamin A?

Answer 6

converted into retinoids to regulate genes and stuff

Question 7

What’s the result of iodine deficiency? What disorders are causes?

Answer 7

Overstimulation of TSH release, which results in…
- Hyperplasia (increased cell number)
- Hypertrophy (increased cell size)

This causes…
- Goiters (adults): thyroid enlargement
- Cretinism (fetus): developmental issues

Question 8

Describe idodine digestion and absorbtion

Answer 8

• can be found free or bound to AAs
• convrted to iodide in the stomach/small intestine and absorbed
• enter cells (mostly thyroid) thru. blood, and uptake is mediated by Na+/I- symporter (NIS)

Question 9

Describe the steps of iodide transport and T4/3 production

Answer 9

• iodide is brought from blood into thyroid colloid by NIS, and is oxidized into a radical
• thyroglobulin (THG) within the colloid is attacked by the radical on its tyrosin residues
• proteases within the colloid then hydrolyze THG, producing T3 and T4 hormones (less T3 than T4)
• T3/4 then are released back into the blood and transported by carrier proteins

Question 10

describe T3/T4 signalling

Answer 10

• any T4 is converted to T3
• T3 enters cytosol and migrates to nucleus
• T3 binds to receptor (THR), which then binds to response elements in the romotr regions of DNA
• induced genes play key roles in ATPases or growth hormones

Question 11

Vitamin A are also called…

Answer 11

retinoids

Question 12

Carotenes are…

Answer 12

vitamin A precursors

Question 13

vitamin A deficiency causes…

Answer 13

• poor epithelial differentiation (causes keratinization and little muscus production in eye – which leaves risk of infection and blindness)
• impaired growth, fertility and development

Question 14

vitamin A toxicity causes…

Answer 14

liver cell death