Oxytocin and anti-diuretic hormone are:

Correct Answer: D

Rationale: The correct answer is D because oxytocin and anti-diuretic hormone are synthesized in the hypothalamus and stored in the posterior pituitary gland before being released into the bloodstream. This process is essential for regulating various physiological functions. Choices A and C are incorrect as oxytocin and anti-diuretic hormone are not complex steroids and are not released from the anterior pituitary. Choice B is also incorrect because while these hormones are indeed synthesized in the posterior pituitary, they are stored in the posterior pituitary before their release.

Correct Answer: D

Rationale: The correct answer is D because synthesis of thyroid hormones (T3 and T4) occurs by the coupling of iodinated tyrosine residues on thyroglobulin within thyroid follicles. Thyroglobulin acts as a precursor for thyroid hormone synthesis. Choices A, B, and C are incorrect because thyroid hormone synthesis does not occur in parafollicular cells, extracellularly in plasma, or require cholesterol for the coupling of iodinated tyrosine residues on thyroglobulin.

Correct Answer: A

Rationale: Aldosterone increases potassium excretion by promoting the reabsorption of sodium and water in the kidneys, leading to potassium excretion. This helps maintain electrolyte balance. Other choices are incorrect because aldosterone does not directly increase water loss, is released in response to low blood volume, and is deficient in Addison's disease.

Correct Answer: C

Rationale: Increased parathyroid hormone (PTH) concentration is associated with tetany because PTH helps regulate calcium levels in the blood. When calcium levels are low, PTH is released to stimulate the release of calcium from bones and increase calcium absorption from the intestines. Tetany is characterized by muscle cramps and spasms due to low calcium levels, which can occur when PTH levels are elevated. A: Vitamin D toxicity is associated with high levels of calcium in the blood, not low calcium levels as seen in tetany. B: Rickets is a condition caused by vitamin D deficiency, leading to impaired bone growth and development, not directly related to elevated PTH levels. D: Reduced excretion of phosphate is not directly linked to elevated PTH levels, as PTH primarily regulates calcium levels.

Correct Answer: C

Rationale: The correct answer is C: Oxytocin. The anterior pituitary gland produces several hormones, including adrenocorticotropic hormone (A), growth hormone (B), and thyroid-stimulating hormone (D). Oxytocin is actually produced by the posterior pituitary gland, not the anterior pituitary. Oxytocin is responsible for uterine contractions during childbirth and milk ejection during breastfeeding. Therefore, C is the correct answer as it is not produced by the anterior pituitary unlike the other hormones mentioned.