If the thyroid gland is unable to produce iodinated thyroglobulin, what is the effect on hormone production?

a) Synthesis of thyroglobulin by the follicular cells: This occurs after iodide has been trapped and transported into the follicular lumen.

b) Oxidation of iodide by the follicular cells: This is a later step; iodide must first be trapped before it can be oxidized into iodine.

c) Coupling of T1 and T2: This is one of the final steps in T₃/T₄ synthesis where iodinated tyrosines are joined.

d) lodide trapping by the follicular cells

Iodide trapping is the first step, where follicular cells actively transport iodide from the bloodstream into the thyroid follicle using sodium-iodide symporters.

a) They cross the plasma membrane.
Amino acid-based hormones are water-soluble and cannot easily cross the lipid bilayer of the plasma membrane.

b) They are lipid soluble.
Unlike steroid hormones, amino acid-based hormones are not lipid-soluble; they are hydrophilic.

c) They are synthesized from cholesterol.
Steroid hormones are synthesized from cholesterol, not amino acid-based hormones.

d) They require a receptor in the plasma membrane.
Due to their inability to cross the plasma membrane, amino acid-based hormones bind to cell surface receptors to trigger intracellular responses via second messengers.