The receptors for non-steroid peptide hormones are found on the ______.

Correct Answer: A

Rationale: The receptors for non-steroid peptide hormones are typically found on the plasma membrane of target cells. These hormones are large or polar molecules that cannot easily diffuse through the cell membrane. Instead, they bind to specific receptors on the cell surface, initiating signaling pathways that eventually lead to changes within the cell. Once the peptide hormone binds to its receptor on the plasma membrane, secondary messenger systems are activated to relay the signal into the cell and initiate the appropriate cellular response. This distinct mechanism of action highlights the importance of the plasma membrane as the location of receptors for non-steroid peptide hormones.

Correct Answer: D

Rationale: Vanillylmandelic acid (VMA) is a metabolite of catecholamines, such as epinephrine and norepinephrine. Phaeochromocytoma is a catecholamine-secreting tumor that arises from the chromaffin cells in the adrenal medulla or sympathetic ganglia. As a result of the increased production of catecholamines in patients with phaeochromocytoma, there is an increase in VMA excretion in the urine. This increase in VMA excretion is a significant diagnostic feature of phaeochromocytoma and helps in its detection through urine testing. Therefore, the correct choice is D. Phaeochromocytoma.

Correct Answer: C

Rationale: Hormones are chemical messengers that are produced by various glands in the body and released into the bloodstream to signal and regulate the activity of specific target cells. Unlike energy sources that can be metabolized for energy production (like carbohydrates and fats), hormones are not typically used as an energy source themselves (Choice B). Hormones are typically not biologically inert by themselves (Choice A), as they have specific functions in regulating various physiological processes in the body. While some hormones may be stored in secretory granules before release, not all hormones are stored in this manner (Choice D). Additionally, hormones are not always released by exocytosis (Choice E), as some hormones can also be released through other mechanisms such as diffusion. The correct choice, therefore, is C: hormones are incorporated as a structural moiety into another molecule, as they bind to specific receptors on target cells to elicit a cellular response and regulate physiological functions.

Correct Answer: A

Rationale: Centripetal obesity, acne, and hirsutism are classic features of Cushing's syndrome. Cushing's syndrome results from prolonged exposure to high levels of cortisol, which can be due to various causes such as adrenal tumors, pituitary adenomas, or exogenous glucocorticoid use. Centripetal obesity refers to the characteristic fat distribution pattern seen in Cushing's syndrome, where fat accumulates mainly in the face, neck, and trunk while sparing the limbs. Acne and hirsutism are also commonly seen in Cushing's syndrome due to the hormonal imbalances caused by excess cortisol. Testing for serum cortisol levels, dexamethasone suppression tests, and imaging studies can help confirm the diagnosis of Cushing's syndrome in a patient presenting with these symptoms.

Correct Answer: D

Rationale: The most common cause of Cushing's syndrome is a pituitary adenoma, specifically a corticotroph adenoma. This adenoma leads to excessive secretion of adrenocorticotropic hormone (ACTH) by the pituitary gland, which in turn stimulates the adrenal glands to produce high levels of cortisol. This results in the symptoms and signs characteristic of Cushing's syndrome. Pituitary adenomas are responsible for around 70-80% of cases of Cushing's syndrome, making it the most common cause.

Correct Answer: A

Rationale: Acromegaly is the condition characterized by the enlargement of the bones of the hands, feet, and face due to the overproduction of growth hormone in adults. This excess growth hormone typically comes from a benign tumor in the pituitary gland, leading to the gradual enlargement of these body parts. Cushing syndrome, on the other hand, is caused by prolonged exposure to high levels of cortisol and is not directly related to bone enlargement. Gigantism is the condition of excessive growth in height due to overproduction of growth hormone occurring in children before the closure of growth plates. Myxedema is a term used to describe severe hypothyroidism and is not directly associated with bone enlargement.

Correct Answer: A

Rationale: Acromegaly is a disorder caused by excessive growth hormone production by the pituitary gland in adults, leading to an increase in muscle mass (hypertrophy). Hoffman syndrome, characterized by increased muscle mass with slowness of activity, is a clinical feature often seen in individuals with acromegaly. The excessive growth hormone levels in acromegaly can cause acral growth, soft tissue swelling, and muscle hypertrophy, contributing to the characteristic features of the condition, including Hoffman syndrome. Therefore, the correct answer is Acromegaly.

Correct Answer: A

Rationale: Tremor (A): Tremors or shaky hands are common symptoms of hyperthyroidism. This is due to the increased metabolic rate caused by excess thyroid hormone in the body.

Correct Answer: C

Rationale: The gold standard for diagnosing acromegaly is the oral glucose tolerance test (OGTT) along with growth hormone (GH) measurement. During this test, the patient is given a glucose solution to drink, and then blood samples are taken to measure GH levels at specific time intervals. In a person without acromegaly, glucose ingestion would typically suppress GH levels. However, in individuals with acromegaly, GH levels remain elevated even after glucose administration due to the inability of glucose to inhibit GH release from the tumor.