The ratio of the volume of red blood cells to the total volume of blood is the definition for

a) Accelerates Ca²⁺ release from bone: This is a function of parathyroid hormone (PTH), not calcitonin.

b) Stimulates Ca²⁺ excretion by the kidneys: While calcitonin may promote calcium excretion slightly, its main action is on bone, not the kidneys.

c) Increases Ca²⁺ deposition in bone: Calcitonin, secreted by the thyroid gland’s parafollicular (C) cells, lowers blood calcium by inhibiting osteoclast activity and enhancing calcium deposition in bones.

d) Stimulates the formation of calcitriol in the kidneys: This is primarily a function of PTH, which promotes the synthesis of active vitamin D (calcitriol) in the kidneys

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.