Endocrine System: Hormones and Glands – NDA Biology PYQs

NDA 2025-II

Q. 1. Iodized salt is a vital part of our diet as it is essential for the synthesis of

(a) Estrogen

(b) Thyroxin

(c) Insulin

(d) Adrenalin

Answer: (b) Thyroxin

Explanation: Thyroxine (T4) is the hormone produced by the thyroid gland. It contains four iodine atoms per molecule and cannot be synthesised without an adequate supply of iodine. Iodine is obtained from the diet: iodized salt is a reliable source. Without sufficient iodine, the thyroid cannot produce enough thyroxine, leading to goitre (enlargement of the thyroid gland) and hypothyroidism. Estrogen, insulin, and adrenaline do not contain iodine. Concept Tested: Iodine is essential for thyroxine synthesis by the thyroid gland

★ JOVIK Exam Insight Iodine → thyroxine → thyroid gland. This is the most tested endocrine fact in NDA. Deficiency of iodine → insufficient thyroxine → goitre. Always link iodine to the thyroid, not the pancreas or adrenal gland.

NDA 2022-II

Q. 2. Which one of the following hormones increases the heartbeat in mammals?

(a) Insulin

(b) Melatonin

(c) Thyroxine

(d) Adrenaline

Answer: (d) Adrenaline

Explanation: Adrenaline (epinephrine) is the “fight-or-flight” hormone secreted by the adrenal medulla. In response to stress or emergency, it increases heart rate, dilates airways, raises blood sugar, and redirects blood to muscles. The increase in heart rate is one of its most direct effects. Insulin lowers blood glucose. Melatonin regulates sleep cycles. Thyroxine regulates metabolic rate: it can affect heart rate indirectly but adrenaline is the direct and primary answer. Concept Tested: Adrenaline (adrenal medulla): the “fight-or-flight” hormone that directly increases heart rate

NDA 2021-II

Q. 3. Which one of the following hormones is responsible for the development of female sexual characters?

(a) Prolactin

(b) Estrogen

(c) Oxytocin

(d) Progesterone

Answer: (b) Estrogen

Explanation: Estrogen is the primary female sex hormone produced by the ovaries. It is responsible for the development of secondary sexual characteristics in females: breast development, widening of hips, pubic hair growth, and the onset of menstruation. Prolactin stimulates milk production after childbirth. Oxytocin causes uterine contractions during labour and stimulates milk ejection. Progesterone prepares the uterine lining for implantation and maintains pregnancy. Concept Tested: Estrogen: responsible for development of female secondary sexual characteristics

NDA 2019-II

Q. 4. Thyroid gland produces a hormone called “Thyroxine” which

(a) controls blood glucose levels.

(b) controls ovulation.

(c) controls metabolic rate.

(d) maintains pregnancy.

Answer: (c) controls metabolic rate.

Explanation: Thyroxine (T4) is produced by the thyroid gland and is the primary regulator of the body’s metabolic rate. It controls how quickly cells use energy, produce proteins, and respond to other hormones. High thyroxine = fast metabolism (hyperthyroidism). Low thyroxine = slow metabolism (hypothyroidism). Blood glucose is regulated by insulin and glucagon. Ovulation is controlled by LH (luteinising hormone). Pregnancy is maintained by progesterone. Concept Tested: Thyroxine: controls metabolic rate; produced by the thyroid gland

NDA 2015-I

Q. 5. Which endocrine gland requires iodine to synthesize a particular hormone whose deficiency may cause goitre disease?

(a) Hypothalamus

(b) Pancreas

(c) Thymus

(d) Thyroid gland

Answer: (d) Thyroid gland

Explanation: The thyroid gland is the endocrine gland that requires iodine to synthesise thyroxine. When iodine is deficient in the diet, the thyroid gland cannot produce enough thyroxine. In response, the pituitary gland keeps releasing TSH (thyroid-stimulating hormone), causing the thyroid gland to enlarge abnormally. This enlargement is called goitre. The hypothalamus produces releasing hormones, the pancreas produces insulin and glucagon, and the thymus is involved in immune development: none require iodine for hormone synthesis. Concept Tested: Thyroid gland requires iodine for thyroxine synthesis; iodine deficiency causes goitre

NDA 2009-II

Q. 6. Which of the following regions/cells in the human body is involved in controlling blood sugar level?

(a) Pituitary gland

(b) Islets of Langerhans

(c) Hypothalamus

(d) Spleen

Answer: (b) Islets of Langerhans

Explanation: The Islets of Langerhans are clusters of endocrine cells in the pancreas. They contain two key cell types: beta cells secrete insulin (which lowers blood glucose) and alpha cells secrete glucagon (which raises blood glucose). Together, insulin and glucagon maintain blood glucose within a narrow range. The pituitary gland controls other endocrine glands. The hypothalamus is involved in temperature, hunger, and releasing hormones. The spleen is involved in immune function and destroying old red blood cells. Concept Tested: Islets of Langerhans (pancreas): secrete insulin (beta cells) and glucagon (alpha cells) to regulate blood glucose

★ JOVIK Exam Insight NDA tests blood glucose regulation repeatedly. The Islets of Langerhans in the pancreas contain: beta cells → insulin (lowers glucose), alpha cells → glucagon (raises glucose). This is distinct from the exocrine pancreas, which secretes digestive enzymes.

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