C: Thyroxine (or tetraiodothyronine) is converted to triiodothyronine in_x000D_target tissues.

B: Hormones are circulating messengers that are transported in blood.  A particular hormone does not necessarily affect every cell in the body. Some (but not all) hormones are released by neurones, for example, in the hypothalamus.

B: The anterior pituitary produces hormones that stimulate other endocrine organs, but the anterior pituitary does not release hormones until directed by the hypothalamus.

C: The hypothalamus controls the secretion of the anterior pituitary by the use of “releasing hormones” and “inhibitory hormones”.

C: Steroids are lipid soluble so diffuse through the plasma membrane to bind to a receptor within the cell.

A: Catecholamines (adrenaline, noradrenaline), dopamine and thyroid hormone are all derived from tyrosine.

D: Hypothalamus secretes regulatory hormones that control endocrine cells in the anterior pituitary gland, produces ADH and oxytocin and contains “autonomic centres” that exert neural control over endocrine cells of the adrenal medullae.

D: Aldosterone promotes the absorption of sodium from the filtrate, while potassium (also a positively charged ion) is secreted to maintain electrical neutrality.

B: The anterior pituitary produces and releases six hormones.

D: Endocrine glands secrete “circulating” hormones, that is, they are secreted into the blood.

A: Thyroid hormones T3 and T4 contain three and four iodine atoms, respectively.

C: The hypothalamus produces peptide hormones.

B: Testosterone is not produced in the pituitary nor does the pituitary contain autonomic centres.

B: ADH and OT are produced in the hypothalamus and transported to the posterior pituitary.

C: As aldosterone is concerned with the absorption of sodium ions, a
“mineral”, and aldosterone is produced by the adrenal cortex; it is termed a mineralocorticoid.

D: The pituitary gland releases peptide hormones which are soluble in blood. The other choices refer to steroid hormones which are insoluble in blood. They require transport via plasma proteins.

A: PTH increases plasma Ca2+ (calcitonin aids in lowering blood calcium).

C: PTH causes increased calcium absorption and hence increases blood calcium level.

C: The acini cells produce digestive enzymes.

C: Thyroxine or thyroid hormone contains iodine.

A: Epinephrine is derived from the amino acid tyrosine (so tyrosine is a wrong answer).

B: Parafollicular (or “C”) cells of the thyroid produce calcitonin which aids in lowering of blood calcium.

D: As steroid hormones are lipid soluble, their receptors are inside the cell as they can cross the plasma membrane.

D: Beta cells of the pancreatic islets produce insulin. The alpha cells produce glucagon.

B: Aldosterone causes reclamation of sodium ions from the filtrate and potassium to be secreted in exchange.