Correct Answer: D

Rationale: Weight gain is a common symptom of Cushing's syndrome due to the excessive production of cortisol, a hormone that regulates metabolism and fat storage. The other symptoms listed, such as easy bruising, acne, and stretch marks, are also characteristic features of Cushing's syndrome. However, weight loss is typically not associated with this condition. In fact, individuals with Cushing's syndrome often experience unexplained and rapid weight gain, especially in the face, abdomen, and upper back (resulting in a characteristic "buffalo hump" appearance), rather than weight loss.

Correct Answer: D

Rationale: An Addisonian crisis, also known as an acute adrenal crisis, is a life-threatening medical emergency that occurs due to severe adrenal insufficiency, leading to a sudden drop in cortisol levels. Cortisol is a vital hormone produced by the adrenal glands, and its deficiency can result in serious symptoms such as hypotension, dehydration, electrolyte imbalances, and shock. If left untreated, an Addisonian crisis can be fatal. Therefore, the correct description of an Addisonian crisis is severe adrenal insufficiency resulting in dangerously low serum cortisol levels.

Correct Answer: B

Rationale: The triad of hyponatremia (low sodium levels in the blood), haemodilution (increased plasma volume), and urine hypertonic to plasma (high urine osmolality compared to blood osmolality) is characteristic of Syndrome of Inappropriate Antidiuretic Hormone (SIADH). In SIADH, there is excessive release of antidiuretic hormone (ADH), also known as vasopressin, leading to water retention by the kidneys and dilutional hyponatremia. This condition results in the body holding onto water, causing hyponatremia and dilution of the blood. The urine being hypertonic compared to plasma indicates that the kidneys are reabsorbing water effectively and concentrating the urine.

Correct Answer: A

Rationale: The posterior pituitary gland secretes anti-diuretic hormone (ADH) and oxytocin, which are produced in the hypothalamus and then transported and stored in the posterior pituitary before being released into the bloodstream. ADH, also known as vasopressin, helps regulate water balance in the body by controlling the reabsorption of water in the kidneys. Oxytocin, on the other hand, plays a role in various reproductive functions such as labor and lactation, as well as social bonding and behavior.

Correct Answer: B

Rationale: Prolactin levels can be increased by various factors, including chest wall trauma, pregnancy, and renal failure. However, hyperthyroidism is not typically associated with elevated prolactin levels. In fact, hyperthyroidism is more commonly associated with decreased levels of prolactin due to the inhibitory effect of thyroid hormones on prolactin secretion. Therefore, all of the options except for hyperthyroidism would be expected to increase prolactin levels.