Final answer:
Thyroid hormones are stored in thyroid follicles, which are spherical structures within the thyroid gland. These follicles contain a colloid that holds the glycoprotein thyroglobulin, essential for hormone production. TSH stimulates hormone release when the body needs them. Therefore, correct answer is b.
Step-by-step explanation:
The spherical structures where thyroid hormones are stored before release are known as thyroid follicles. These follicles are lined with a simple cuboidal epithelium and contain a viscous fluid called colloid.
The colloid stores the glycoprotein thyroglobulin, which is the precursor to the thyroid hormones T3 (triiodothyronine) and T4 (thyroxine). Thyroid follicular cells absorb iodine and use it along with thyroglobulin to produce thyroid hormones.
When the body requires thyroid hormones, thyroid-stimulating hormone (TSH) from the anterior pituitary gland stimulates endocytosis of the colloid back into the follicular cells.
Lysosomal enzymes then break apart the thyroglobulin, releasing T3 and T4, which then diffuse into the bloodstream to exert their metabolic effects.