Under secretion of thyroxine before maturity causes an abnormality known as

Step 1: Analyze the question The question asks about under secretion (hyposecretion) of thyroxine before maturity, meaning during childhood or infancy.

Step 2: Concept Thyroxine is produced by the thyroid gland. It controls metabolic rate, growth, and mental development.

• Hyposecretion in children (before maturity): Cretinism. It causes stunted growth, mental retardation, a protruding tongue, a pot belly, and a dull appearance.
• Hyposecretion in adults (after maturity): Myxoedema. It causes a slow metabolic rate, weight gain, dry skin, and sluggishness.
• Hypersecretion: Exophthalmic goitre (Graves' disease), with a high metabolic rate, weight loss, and bulging eyes.
• Gigantism: Over-secretion of growth hormone before maturity (pituitary gland).
• Dwarfism: Under-secretion of growth hormone (pituitary gland). It gives short stature but normal mental development.

Step 3: Eliminate the options

• A. Cretinism: correct, since it is thyroxine deficiency in childhood.
• B. Gigantism: wrong, caused by excess growth hormone.
• C. Dwarfism: wrong, caused by a growth hormone deficiency, not thyroxine.
• D. Myxoedema: this is thyroxine deficiency, but in adults, so it does not fit "before maturity."
• E. Obesity: not a specific thyroxine-deficiency disorder of childhood.

Step 4: Answer The correct answer is A. Cretinism.

Exam tip: Remember "Cretinism = Child" and "Myxoedema = Mature (adult)." Both come from low thyroxine, so the age given in the question decides which one it is.