Where is iodide located in the thyroid gland?

a) Lumen of follicle: Iodide is actively transported into follicular cells, then secreted into the follicular lumen, where it becomes oxidized and incorporated into thyroglobulin during the synthesis of thyroid hormones (T3 and T4).

b) Secretory vesicles inside follicular cells: These vesicles may contain thyroglobulin, but iodide is concentrated in the lumen for hormone synthesis.

c) Golgi apparatus of parafollicular cells: Parafollicular (C) cells produce calcitonin, not thyroid hormones.

d) Cytoplasm of follicular cells: While iodide is transported into the cytoplasm briefly, its major functional location is in the lumen.

a) Stimulates the formation of white blood cells: This is associated with bone marrow and not parathyroid hormone (PTH).

b) Parathyroid hormone (PTH) increases blood calcium levels by stimulating bone resorption, increasing calcium reabsorption in the kidneys, and activating vitamin D to increase calcium absorption from the gut.

c) Increases the level of sodium ions in the blood: Aldosterone regulates sodium levels, not PTH.

d) Increases the level of potassium ions in the blood: This is also regulated by aldosterone and the kidneys, not PTH.

e) Increases the level of glucose in the blood: Glucagon and cortisol are more directly involved in increasing blood glucose.