A patient presents with weight loss, sweating, palpitations, tachycardia, tremors, lid lag, exopthalmosis, and a goiter. Upon taking a thyroid scan, there appears to be an increased amount of iodine. What is the pathogenesis of his disease?

Correct Answer: A

Rationale: The correct answer is A: Autoimmune Mediated. In this case, the patient is presenting with symptoms of hyperthyroidism along with a goiter, which is indicative of Graves' disease, an autoimmune disorder where antibodies stimulate the thyroid gland to produce excess thyroid hormones. The presence of increased iodine uptake in the thyroid scan supports this diagnosis. On the other hand, immune complex mediated diseases typically involve tissue damage caused by immune complexes, not thyroid hormone excess. The cause being unknown or infection-related are not consistent with the symptoms and thyroid scan findings in this case.

Correct Answer: B

Rationale: Step 1: Antidiuretic hormone (ADH) is released by the posterior pituitary, and its main function is to increase water reabsorption in the kidneys, leading to decreased urine volume and increased blood volume. Step 2: If ADH causes urine volume to increase and blood volume to decrease, it would be counterproductive to its known physiological role. Step 3: Therefore, Choice B is false as it contradicts the established function of ADH. Summary: - Choice A is true because oxytocin and antidiuretic hormone are indeed produced in the hypothalamus and stored in the posterior pituitary. - Choice C is true as luteinizing hormone does trigger ovulation and stimulates the production of progesterone and some estrogens. - Choice D is true because hyposecretion of follicle-stimulating hormone or luteinizing hormone can lead to infertility in both males and females.

Correct Answer: A

Rationale: The correct answer is A: somatotropin. The growth hormone produced by the pituitary gland is known as somatotropin. - "Somato" refers to the body, indicating its role in regulating body growth. - "Tropin" refers to stimulation, emphasizing its function in promoting cell growth and regeneration. - Prolactin (B) is responsible for milk production. - Luteinizing hormone (C) and follicle-stimulating hormone (D) are involved in reproductive functions, not growth regulation.

Correct Answer: A

Rationale: The correct answer is A: Thyroid hormone. Thyroid hormone acts on its target tissues by a steroid hormone mechanism of action because it is a lipid-soluble hormone that can diffuse through cell membranes and bind to intracellular receptors. These hormone-receptor complexes then directly regulate gene expression. In contrast, choices B, C, and D do not follow a steroid hormone mechanism of action. Parathyroid hormone (PTH) acts through G-protein coupled receptors, Antidiuretic hormone (ADH) acts through V2 receptors, and β1 adrenergic agonists act through beta-adrenergic receptors, which are all distinct from the mechanism of action of steroid hormones.

Correct Answer: D

Rationale: The correct answer is D because growth hormone promotes long bone growth during the formative years by stimulating the growth plates in bones. This hormone plays a crucial role in skeletal growth and development. Choice A is incorrect because somatostatin is a different hormone that inhibits growth hormone release. Choice B is incorrect because growth hormone is primarily regulated by neural mechanisms. Choice C is incorrect because growth hormone actually promotes muscle growth and reduces fat mass.