Iodine

Question 1

How is Iodine absorbed?

Answer 1

In the small intestine
Goitrogens in foods make iodine more difficult to absorb
- turnips, cabbage, brussel sprouts, broccoli
- cooked states of these foods decreases goitrogen activity

Question 2

How is Iodine transported?

Answer 2

Bound to thyroglobulin and is taken to the thyroid gland

Sodium-dependent transport system traps iodine in thyroid gland for hormone synthesis

Question 3

Where is Iodine stored?

Answer 3

Muscle, thyroid gland, skin

Question 4

What are the functions of Iodine?

Answer 4

Iodine does not function on its own, it is a part of T3 and T4

T4 is the circulating form of thyroid hormone

T3 is the active form of thyroid hormone

T4 converted to T3 in cells by iodothyronine-deiodinases (DIOs) , a selenium requiring metalloenzyme

Question 5

What are the functions of thyroid hormone?

Answer 5

Basal energy expenditure (basal metabolic rate)
• Energy metabolism
• Growth and development in the foetus /infant:
• Brain and nervous system development
• Full organ growth and maturation

Question 6

What is the result of an Iodine deficiency?

Answer 6

Goitre: when T4 drops there is increased TSH secreted, thyroid enlarges to trap more iodine, slowed metabolism

Neurological Cretinism: irreversible mental retardation, loss of hearing and speech abilities, muscle spasticity can all occur if the mother is iodine deficient whilst pregnant

Question 7

What occurs in Iodine toxicity?

Answer 7

Enlarged thyroid gland too: hypothyroidism and hyperthyroidism lead to decreased and increased thyroid hormone synthesis respectively, leading to a goitre development

Question 8

What are good sources of Iodine?

Answer 8

• Seaweed
• Plain yoghurt
• Cottage cheese
• Milk
• Iodised table salt