Hypothyroidism in adults due to an underactive thyroid is ____.

Correct Answer: C

Rationale: The correct answer is C: myxedema. Hypothyroidism in adults is commonly caused by an underactive thyroid gland, leading to decreased production of thyroid hormones. Myxedema is the term used to describe severe hypothyroidism, characterized by symptoms such as fatigue, weight gain, cold intolerance, and swelling of the face and hands. Graves disease (choice A) is actually a cause of hyperthyroidism, not hypothyroidism. Diabetes insipidus (choice B) is a disorder related to the kidneys and has no direct connection to thyroid function. Acromegaly (choice D) is caused by excess growth hormone production, unrelated to thyroid function. Therefore, the correct choice is C as it accurately describes hypothyroidism in adults.

Correct Answer: C

Rationale: The correct answer is C, tumor angiogenesis factor. Cancer cells release this growth factor to promote the formation of new blood vessels (angiogenesis) around the tumor, providing a supply of nutrients and oxygen to support their growth. This process is essential for cancer progression. A: Macrophage colony-stimulating factor is involved in the production and differentiation of macrophages, not in angiogenesis. B: Platelet-derived growth factor promotes cell growth and division, but it is not specifically responsible for angiogenesis in the context of cancer. D: Epidermal growth factor is a signaling molecule that promotes cell proliferation and differentiation but is not the primary factor released by cancer cells to induce angiogenesis.

Correct Answer: B

Rationale: The correct answer is B: Androgens. Androgens are male sex hormones responsible for male characteristics like facial hair growth and deepening of voice. Aldosterone (A) is a mineralocorticoid hormone, not a sex hormone. Pheromones (C) are chemical signals, not hormones. Insulin (D) is a hormone that regulates blood sugar levels, not related to sex characteristics. Therefore, B is the correct choice for a male sex hormone.

Correct Answer: D

Rationale: The correct answer is D: Parathyroid hormone. Parathyroid hormone plays a crucial role in regulating calcium homeostasis by increasing calcium levels in the blood through various mechanisms. It promotes calcium release from bones, enhances calcium absorption in the intestines, and reduces calcium excretion from the kidneys. Insulin (Choice A) primarily regulates blood sugar levels, not calcium. Erythropoietin (Choice B) stimulates red blood cell production and does not directly affect calcium homeostasis. Aldosterone (Choice C) regulates sodium and potassium balance but not calcium levels. Thus, Parathyroid hormone is the correct choice for controlling calcium homeostasis.

Correct Answer: C

Rationale: The correct answer is C: luminal acid. Gastrin secretion is primarily stimulated by the presence of luminal peptides and vagal discharge. Luminal acid inhibits gastrin secretion through negative feedback mechanisms. Phenylalanine does not directly stimulate gastrin secretion. In summary, luminal acid is the correct answer because it acts as an inhibitory factor for gastrin secretion, whereas the other choices are known stimulatory factors.