Question

Normal functioning of thyroid gland require certain quantity of daily in take of iodine. What is its normal daily requirement ?

• A. 1 - 2 mg
• B. 2 - 5 mg
• C. 100 - 200 \(\mu\)g
• D. 400 - 500 \(\mu\)g

Hint:

A simple way to remember micronutrient units: Iodine is a 'trace' mineral, meaning it is required in micrograms (\(\mu\)g), unlike 'macrominerals' like calcium or magnesium which are needed in milligrams (mg) or grams.

Answer 1

The Correct Option is C

Step 1: Concept:
The question asks for the clinically recommended daily dietary intake of the trace element iodine necessary for maintaining healthy thyroid function.

Step 2: Step-by-step Explanation:

• The thyroid gland is a vital endocrine organ located in the neck. Its primary physiological role is the synthesis and secretion of thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3).

• Iodine is an irreplaceable structural component of these hormones. T4 contains four iodine atoms, and T3 contains three iodine atoms.

• Since the human body cannot synthesize iodine endogenously, it must be absorbed entirely from the diet.

• To synthesize adequate amounts of these hormones to maintain a eumetabolic state, the thyroid gland continuously traps circulating iodide from the bloodstream.

• According to major health organizations, including the World Health Organization (WHO), the standard recommended dietary allowance (RDA) of iodine for healthy human adults is \( 150 \, \mu\text{g} \) per day.

• This requirement increases slightly during periods of rapid growth or heightened metabolic demand, such as during pregnancy and lactation, where the recommendation ranges between \( 220 \) to \( 290 \, \mu\text{g} \) per day.

• When evaluating the provided options, the range of \( 100 - 200 \, \mu\text{g} \) perfectly brackets the standard adult requirement of \( 150 \, \mu\text{g} \).

• The other options present values that are either massively excessive (milligram range, which could induce iodine toxicity or Wolff-Chaikoff effect) or too high for baseline daily intake (\(400 - 500 \, \mu\text{g}\)).

Step 3: Final Answer:
The normal daily dietary requirement is 100 - 200 \(\mu\)g.