Final answer:
The master gland that the physician mentions is the pituitary gland, which controls other endocrine glands like the thyroid, adrenal glands, and gonads. It operates in conjunction with the hypothalamus, influencing various physiological processes through the production of hormones. Hyposecretion is inadequate hormone production as seen in hypothyroidism, while hypersecretion is excessive hormone production, as in Cushing's syndrome.
Step-by-step explanation:
When a physician speaks of the "master gland," they are referring to the pituitary gland, option A. This endocrine gland has a critical role in controlling various other glands within the endocrine system. Hormones produced by the pituitary gland include those that stimulate the thyroid gland, the adrenal glands, and the gonads (ovaries and testes). These hormones are often referred to as tropic hormones because they regulate the secretion of hormones by these target glands.
The main brain structure that secretes hormones controlling the pituitary gland is the hypothalamus. Hyposecretion is the condition of insufficient hormone production, and an example of this is hypothyroidism, which involves inadequate production of thyroid hormones by the thyroid gland. Conversely, Cushing's syndrome is an example of hypersecretion, where too much cortisol is produced by the adrenal glands. Additionally, the immune system is closely tied to endocrine function, with the thymus gland playing a prominent role. Lastly, it is false that the hypothalamus is the master gland; it is however, a major regulatory structure for the pituitary gland.