A child is diagnosed with both iodine deficiency and a deficiency of growth hormone secreted by the pituitary gland. Both conditions affect growth, yet the underlying reasons differ.
(i) Name the hormone whose synthesis is impaired by iodine deficiency and explain how its deficiency leads to a visible symptom in the child.
(ii) Explain how a deficiency of growth hormone leads to a different growth-related outcome compared to iodine deficiency.
(iii) The pituitary gland is often called the 'master gland'. Based on the above scenario, justify this title and explain how the pituitary's control over another gland illustrates the concept of hormonal feedback regulation in the body.
Generated by claude-sonnet-4-6 · 2026-06-26 01:03 · grounding rag
Model Answer
(i) Iodine deficiency impairs the synthesis of thyroxine (thyroid hormone). Without sufficient thyroxine, the thyroid gland keeps receiving signals to produce more hormone and enlarges abnormally. This causes a visible swelling in the neck called goitre.
(ii) Deficiency of growth hormone (from the pituitary) leads to stunted growth — the child remains shorter than normal due to insufficient stimulation of body tissues for growth. Unlike goitre (which is a glandular swelling), this deficiency causes reduced overall body size without any visible glandular enlargement.
(iii) The pituitary is called the 'master gland' because it controls other endocrine glands, including the thyroid. It releases hormones that stimulate the thyroid to secrete thyroxine. When thyroxine levels are adequate, they signal back to the pituitary to reduce stimulation — this is hormonal feedback regulation, ensuring hormone levels stay balanced in the body.
Source: Chapter 6 — Control and Coordination; Chapter 7 — Reproduction (Endocrine system references)
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Explanation
- (i) Examiners expect "thyroxine" named explicitly and "goitre" as the visible symptom.
- (ii) The key contrast is: iodine deficiency → gland swelling; GH deficiency → stunted/dwarfism. Mentioning this contrast earns the comparison mark.
- (iii) Two things are needed: why pituitary is "master" (it controls other glands) AND feedback mechanism (product hormone signals back to reduce further secretion). Both are required for full marks.
- Keep language simple and factual — CBSE rewards accuracy over elaboration.