The body’s major metabolic hormone is released from the:

Correct Answer: B

Rationale: The correct answer is B: Thyroid. The body's major metabolic hormone, thyroxine (T4) and triiodothyronine (T3), is released from the thyroid gland. The thyroid gland plays a crucial role in regulating metabolism. Pituitary (A) releases various hormones but not the major metabolic hormone. Thymus (C) is responsible for immune function, not metabolism. Hypothalamus (D) regulates the pituitary gland but does not directly release the major metabolic hormone.

Correct Answer: A

Rationale: The correct answer is A: enzyme. Endocrine glands are stimulated by three main categories: humoral (based on blood levels of certain substances), neural (stimulation by nerves), and hormonal (stimulation by other hormones). Enzymes do not directly stimulate endocrine glands. They are biological catalysts that facilitate biochemical reactions, not a category of stimulus for endocrine glands. Therefore, A is the correct answer. Choices B, C, and D are incorrect as they are valid categories of endocrine gland stimulus based on blood levels, nerves, and hormones respectively.

Correct Answer: C

Rationale: The correct answer is C because insulin is released when the body's glucose level rises. This is a key function of insulin to regulate blood sugar levels. When glucose levels increase after a meal, beta cells release insulin to help cells absorb and use glucose for energy. This process helps to maintain blood sugar within a healthy range. Choice A is incorrect because insulin release is not necessarily excessive in obese people, but rather it can be impaired due to insulin resistance. Choice B is incorrect because insulin is typically released in response to high blood sugar levels, not physical stress. Choice D is incorrect because insulin is released when blood sugar levels drop too low, not rise.

Correct Answer: C

Rationale: The correct answer is C: epinephrine. Steroid-based hormones are derived from cholesterol and include estrogen, aldosterone, and cortisone. Epinephrine is a catecholamine hormone, not a steroid hormone. Catecholamines are derived from the amino acid tyrosine, not cholesterol like steroid hormones. Therefore, epinephrine does not belong to the category of steroid-based hormones.

Correct Answer: A

Rationale: The correct answer is A: liver. Thyroid hormone affects the liver by regulating metabolism and energy production. It increases the breakdown of fats, proteins, and carbohydrates. The liver plays a crucial role in converting thyroid hormones into their active form. Summary: B: The spleen is not directly affected by thyroid hormone. C: The thyroid gland produces thyroid hormone but is not directly affected by it in adults. D: While the brain is indirectly influenced by thyroid hormone, it is not a primary target organ for its effects in adults.