Questions & explanations
1. Which ovarian hormone is primarily responsible for supporting pregnancy and promoting milk gland development?
- A. Estrogen
- B. Progesterone
- C. Relaxin
- D. Inhibin
Answer: B. Progesterone
Progesterone is secreted by the ovary (corpus luteum) and plays a key role in maintaining pregnancy by supporting the uterine lining and promoting the development of milk glands (mammary glands) in preparation for lactation. Estrogen (A) stimulates growth of female secondary sex organs and characters but is not the primary hormone for pregnancy support. Relaxin (C) helps relax pelvic ligaments during childbirth, and inhibin (D) inhibits FSH secretion; neither is primarily responsible for supporting pregnancy or milk gland development.
2. Which of the following correctly describes the role of testosterone in males?
- A. It is secreted by the anterior pituitary and stimulates spermatogenesis
- B. It is an androgen that regulates the development and function of male accessory sex organs and promotes spermatogenesis
- C. It is produced by the seminal vesicles and maintains secondary sexual characteristics
- D. It inhibits the secretion of FSH and LH through positive feedback
Answer: B. It is an androgen that regulates the development and function of male accessory sex organs and promotes spermatogenesis
Testosterone is the main androgen secreted by the testes. It is responsible for the development, maturation, and function of male accessory sex organs (e.g., prostate, seminal vesicles) and stimulates spermatogenesis. Option A is incorrect because testosterone is secreted by the testes, not the anterior pituitary. Option C is incorrect because testosterone is produced by the testes, not the seminal vesicles. Option D is incorrect because testosterone exerts negative feedback on FSH and LH secretion, not positive feedback.
3. Steroid hormones like testosterone exert their effects by:
- A. Binding to membrane-bound receptors and generating second messengers
- B. Diffusing through the cell membrane and binding to intracellular receptors that regulate gene expression
- C. Activating G-proteins on the cell surface
- D. Opening ion channels directly on the plasma membrane
Answer: B. Diffusing through the cell membrane and binding to intracellular receptors that regulate gene expression
Steroid hormones (e.g., testosterone, estrogen) are lipid-soluble and diffuse across the cell membrane. They bind to intracellular receptors (often nuclear receptors), and the hormone-receptor complex acts as a transcription factor to regulate gene expression. Option A describes the mechanism of protein/peptide hormones. Option C is associated with some peptide hormones via G-protein coupled receptors. Option D is typical of neurotransmitters like acetylcholine at ion channels, not steroid hormones.
4. Which of the following is an example of a second messenger generated by the binding of a peptide hormone to its membrane-bound receptor?
- A. Testosterone
- B. Cyclic AMP
- C. Thyroxine
- D. Estrogen
Answer: B. Cyclic AMP
Peptide hormones (e.g., insulin, glucagon) bind to membrane-bound receptors and activate intracellular signaling pathways that produce second messengers such as cyclic AMP (cAMP), IP3, or calcium ions. Cyclic AMP is a classic second messenger that mediates the effects of many peptide hormones. Testosterone (A), thyroxine (C), and estrogen (D) are steroid or thyroid hormones that act via intracellular receptors, not membrane-bound receptors generating second messengers.
5. Which of the following is NOT a function of cortisol?
- Maintenance of cardiovascular system
- Anti-inflammatory action
- Stimulation of milk secretion from mammary glands
- Stimulation of red blood cell production
Answer: Stimulation of milk secretion from mammary glands
Cortisol (a glucocorticoid) maintains the cardiovascular system and kidney function, has anti-inflammatory action, suppresses the immune response, and stimulates RBC production. It plays no role in milk secretion, which is controlled by prolactin and oxytocin. So 'stimulation of milk secretion' is NOT a function of cortisol.
6. Which of the following best defines a hormone?
- A chemical signal that travels through the blood to a distant target where it produces a response
- An electrical impulse that travels along neurons to a target cell
- A local mediator that acts on adjacent cells without entering the bloodstream
- A substance secreted into the environment to communicate with other organisms
Answer: A chemical signal that travels through the blood to a distant target where it produces a response
Hormones are chemical messengers secreted by endocrine glands into the bloodstream, which carry them to distant target organs or cells where they elicit a specific response. This distinguishes them from neural signals (electrical impulses) and local mediators (paracrine/autocrine signals).
7. Hypothyroidism during pregnancy can result in the baby developing which condition characterized by stunted growth, mental retardation, and deaf-mutism?
- A. Myxedema
- B. Cretinism
- C. Graves' disease
- D. Acromegaly
Answer: B. Cretinism
Cretinism is caused by severe hypothyroidism in infancy/childhood, often due to maternal iodine deficiency during pregnancy, leading to physical and mental retardation. Myxedema is adult hypothyroidism, Graves' disease is hyperthyroidism, and acromegaly is from excess growth hormone.
8. Which hormones are collectively called gonadotropins?
- Growth hormone and prolactin
- TSH and ACTH
- LH and FSH
- Oxytocin and vasopressin
Answer: LH and FSH
Luteinising hormone (LH) and follicle-stimulating hormone (FSH) are gonadotropins that stimulate gonadal activity. GH and PRL are not gonadotropins; TSH and ACTH are tropic hormones for thyroid and adrenal; oxytocin and vasopressin are posterior pituitary hormones.
9. A 35-year-old patient presents with weight loss, weakness, hyperpigmentation, and hypotension. Which endocrine disorder is most likely responsible?
- Cushing's syndrome
- Addison's disease
- Graves' disease
- Cretinism
Answer: Addison's disease
Addison's disease results from hyposecretion of adrenal cortex hormones, causing weight loss, weakness, hyperpigmentation, and hypotension. Cushing's syndrome involves excess cortisol, Graves' disease is hyperthyroidism, and cretinism is childhood hypothyroidism.
10. Enlargement of the thyroid gland due to cancer or nodules can lead to:
- A. Hypothyroidism
- B. Hyperthyroidism
- C. Decreased basal metabolic rate
- D. Reduced iodine uptake
Answer: B. Hyperthyroidism
Thyroid cancer or nodules can cause excessive production of thyroid hormones, resulting in hyperthyroidism. This increases BMR and iodine uptake, not decrease them. Hypothyroidism is not typical; it's more common in iodine deficiency or autoimmune destruction.
11. Which hormone stimulates vigorous contraction of the uterus during childbirth and milk ejection from mammary glands?
- Prolactin
- Oxytocin
- Estrogen
- Progesterone
Answer: Oxytocin
Oxytocin acts on smooth muscles of the uterus to cause contractions during labor and on mammary glands for milk ejection. Prolactin stimulates milk production, not ejection. Estrogen and progesterone prepare the uterus but do not directly cause contractions.
12. Iodine deficiency in the diet commonly leads to:
- A. Hyperthyroidism and exophthalmos
- B. Hypothyroidism and enlargement of the thyroid gland (goitre)
- C. Increased basal metabolic rate
- D. Decreased TSH secretion
Answer: B. Hypothyroidism and enlargement of the thyroid gland (goitre)
Lack of iodine reduces thyroid hormone production, causing hypothyroidism. The pituitary increases TSH to stimulate the thyroid, leading to gland enlargement (goitre). Hyperthyroidism, increased BMR, and decreased TSH are not typical of iodine deficiency.