Hormone Regulation of Metabolism

This question requires identifying three key components related to hormone function: a hormone that regulates carbohydrate, protein, and fat metabolism (A), the endocrine gland that secretes this hormone (B), and a dietary factor that influences the gland's function (C).

Hormone (A): Regulator of Body Metabolism

We need to find the hormone primarily responsible for controlling the body's metabolic rate, affecting how energy is used and how nutrients like carbohydrates, proteins, and fats are processed.

• Thyroxine: This hormone, produced by the thyroid gland, is well-known for its role in regulating the basal metabolic rate. It impacts cellular metabolism significantly, influencing the breakdown and utilization of all major macronutrients.
• Growth hormone: While influencing metabolism, its primary role is growth and tissue repair.
• Insulin: Primarily manages blood glucose levels (carbohydrate metabolism) and is less central to the regulation of protein and fat metabolism in the context described.
• Adrenaline: Acts as a short-term stress hormone, boosting metabolism rapidly but not for sustained regulation.

Therefore, Thyroxine is the hormone that best fits the description of regulating carbohydrate, protein, and fat metabolism.

Gland (B): Source of Thyroxine

The hormone Thyroxine is secreted by a specific gland within the endocrine system. Identifying this gland is the next step.

• The Thyroid gland, located in the neck region, is responsible for synthesizing and releasing thyroid hormones, including Thyroxine (T4) and Triiodothyronine (T3). These hormones are essential for metabolic regulation.

Consequently, the gland (B) is the Thyroid gland.

Dietary Factor (C): Impacting Thyroid Function

The final part of the question asks for a dietary component that affects the functioning of the gland identified in step 2 (the Thyroid gland).

• Iodine: This mineral is a critical component required for the synthesis of thyroid hormones (Thyroxine and T3). Insufficient intake of dietary Iodine can impair the thyroid gland's ability to produce these hormones, leading to conditions like hypothyroidism.
• Proteins: Essential nutrients, but not directly required as a building block for thyroid hormones like iodine is.
• Sugar: Primarily affects energy balance and insulin response, not thyroid hormone synthesis.
• Salts: A general term; while essential, it's the specific element Iodine (often found in iodized salt) that is crucial for thyroid function.

Thus, Iodine in the diet is a key factor impacting the Thyroid gland's function.

Summary of Components

Based on the analysis:

• (A) Hormone: Thyroxine
• (B) Gland: Thyroid
• (C) Dietary Factor: Iodine

These three components correctly fill the blanks in the question statement.