The Glucagon is:

Correct Answer: A

Rationale: The correct answer is A because glucagon stimulates the breakdown of glycogen into glucose, increasing blood glucose levels. Glucagon does not slow down glucose formation from lactic acid (B), decrease glycogen conversion (C), or speed up protein synthesis (D). Glucagon's primary function is to raise blood glucose levels in response to low blood sugar levels.

Correct Answer: C

Rationale: The correct answer is C: Iodine. Iodine is essential for the production of thyroid hormones T3 and T4. These hormones regulate metabolism, growth, and development. Potassium (A), Sodium (B), and Calcium (D) do not play a direct role in thyroid function. Potassium and Sodium are electrolytes important for nerve function and fluid balance, while Calcium is crucial for bone health and muscle function. Therefore, the correct answer is Iodine as it is specifically required for normal thyroid function.

Correct Answer: D

Rationale: The correct answer is D: Both A & B. The thyroid and parathyroid glands work together to regulate calcium levels in the blood. The parathyroid gland releases parathyroid hormone, which increases calcium levels, while the thyroid gland secretes calcitonin, which decreases calcium levels. Therefore, both glands play a crucial role in maintaining calcium homeostasis. Choice A, the thyroid gland, is incorrect as it primarily regulates metabolism. Choice C, the adrenal medulla, is incorrect as it is responsible for releasing adrenaline and noradrenaline, not regulating calcium levels.

Correct Answer: B

Rationale: The correct answer is B: Weight gain. Addison's disease is characterized by adrenal insufficiency, leading to symptoms such as salt craving, hypoglycemia, and hyperpigmentation due to increased melanin production. Weight loss, not weight gain, is commonly associated with Addison's disease due to decreased cortisol levels. Salt craving is due to sodium loss, hypoglycemia results from insufficient cortisol levels, and hyperpigmentation is caused by elevated ACTH levels stimulating melanin production. Weight gain is not a typical symptom, making it the correct answer.

Correct Answer: D

Rationale: The correct answer is D, receptor-mediated stimulus. Hormones can be stimulated by hormonal, humoral, or neural factors, but not directly by receptors. Hormonal stimulus involves other hormones triggering hormone release, humoral stimulus involves changing blood levels of ions or nutrients triggering hormone release, and neural stimulus involves direct nerve stimulation triggering hormone release. Receptor-mediated stimulus is not a recognized type of hormone stimulus because hormones do not directly respond to receptors in this context.