G-proteins (guanine nucleotide-binding proteins) are molecules involved in the transmission of hormonal signals from outside a cell to the interior by means of a process called:

Correct Answer: A

Rationale: Signal transduction transmits hormonal signals via G-proteins (e.g., in glucagon response), converting extracellular messages into intracellular actions (cAMP) core process. Signal conduction is neural, not hormonal electric impulse. Signal targeting isn't a term receptor specificity fits, but not process. Local signaling is paracrine, not G-protein-mediated typically. Transduction's role distinguishes it, critical for hormone effects across membranes, unlike conduction, vague, or local errors.

Correct Answer: D

Rationale: Growth hormone (GH) is the most abundant anterior pituitary hormone, driving growth and metabolism not LH (reproduction), TSH (thyroid), or ACTH (adrenal). Its high output reflects somatotroph prevalence, distinguishing its systemic role, a NEET key point contrasting with less abundant tropic hormones.

Correct Answer: D

Rationale: A hormone is a chemical produced by an endocrine gland, released into the bloodstream, and transported to distant target cells where it regulates physiological processes, like insulin from the pancreas controlling blood glucose elsewhere. Duct transport fits exocrine glands (e.g., sweat), not hormones. Many effects apply to some hormones (e.g., cortisol), but it's not definitive specificity matters. Gland secretion is true but incomplete transport and action define hormones, not just origin. The full description captures hormones' endocrine nature, distinguishing them from local or ducted secretions, key to their systemic regulatory role.

Correct Answer: C

Rationale: Oxytocin and ADH (vasopressin), synthesized in the hypothalamus, are stored and released from the posterior pituitary (neurohypophysis), regulating childbirth, lactation, and water balance. Adenohypophysis (anterior pituitary) produces hormones like ACTH, not storing these. Kidneys respond to ADH, not store it. Posterior pituitary's neural extension role distinguishes it, critical for hypothalamic hormone delivery, unlike glandular or target organs.

Correct Answer: D

Rationale: Parathyroid hormone (PTH) targets kidneys (Ca²⁺ reabsorption), bones (Ca²⁺ release), and intestines (via vitamin D for Ca²⁺ uptake) to raise blood calcium. Muscles aren't direct targets PTH doesn't alter their function, though low calcium from PTH absence causes tetany indirectly. 'None' is incorrect PTH affects listed organs. Muscles' exclusion distinguishes them, key to PTH's calcium-focused action, unlike regulated sites.