All of the following are associated with increased levels of total T4 in the plasma with a normal free T4 except:

Correct Answer: A

Rationale: The correct answer is A: Cirrhosis. In cirrhosis, there is a decrease in the binding proteins for T4, leading to decreased total T4 levels in the plasma. Pregnancy, euthyroid sick syndrome, and familial excess thyroid binding globulin are all conditions associated with increased total T4 levels due to various physiological changes. In pregnancy, there is an increase in thyroid hormone production to support fetal development. Euthyroid sick syndrome is a condition where there is a decrease in binding proteins, leading to an increase in free T4 levels but normal total T4 levels. Familial excess thyroid binding globulin causes an increase in total T4 levels due to excessive binding proteins.

Correct Answer: B

Rationale: The correct answer is B: Cortisol. The adrenal cortex produces cortisol, a steroid hormone involved in stress response and metabolism. Norepinephrine (A) is produced by the adrenal medulla. 5-DHEA (C) is a precursor to sex hormones and not directly produced by the adrenal cortex. Aldosterone (D) is produced by the adrenal cortex but is involved in regulating salt and water balance, not directly related to cortisol production.

Correct Answer: B

Rationale: The correct answer is B: Bitemporal Hemianopsia. Pituitary adenomas can compress the optic chiasm, leading to bitemporal hemianopsia. This occurs due to the loss of peripheral vision on both sides. Carpo-pedal spasm (A) is associated with hypocalcemia, Chvostek's sign (C) is a facial spasm seen in hypocalcemia, and tremor (D) can be seen in conditions such as Parkinson's disease, but they are not specific to pituitary adenoma. Bitemporal hemianopsia is a classic sign of pituitary adenoma due to its location near the optic chiasm.

Correct Answer: C

Rationale: The correct answer is C: Oxytocin. The anterior pituitary gland produces several hormones, including adrenocorticotropic hormone (A), growth hormone (B), and thyroid-stimulating hormone (D). Oxytocin is actually produced by the posterior pituitary gland, not the anterior pituitary. Oxytocin is responsible for uterine contractions during childbirth and milk ejection during breastfeeding. Therefore, C is the correct answer as it is not produced by the anterior pituitary unlike the other hormones mentioned.

Correct Answer: D

Rationale: Step-by-step rationale: 1. Gynaecomastia is a known side effect of spironolactone, digitalis, and cimetidine. 2. Rifampicin is not associated with gynaecomastia. 3. Rifampicin is an antibiotic used to treat tuberculosis and other infections. 4. The mechanism of action of rifampicin does not involve hormonal changes that could lead to gynaecomastia. Summary of incorrect choices: - A: Spironolactone is a potassium-sparing diuretic that can cause gynaecomastia. - B: Digitalis (digoxin) can lead to gynaecomastia as a side effect. - C: Cimetidine, an H2 receptor antagonist, is also known to cause gynaecomastia.

Correct Answer: D

Rationale: The correct answer is D: Thyroxine-binding globulin (TBG). TBG is the primary source of bound T4 in the plasma as it specifically binds to and transports thyroid hormones. This protein has the highest affinity for T4 compared to other plasma proteins. Albumin (A) and gamma globulins (B) can also bind to thyroid hormones, but TBG is the primary carrier. Thyroid peroxidase (C) is an enzyme involved in thyroid hormone production, not in binding T4 in the plasma.

Correct Answer: C

Rationale: Leydig cells are found in the testes and are responsible for producing testosterone, a crucial male sex hormone. This hormone is essential for the development of male reproductive organs, secondary sexual characteristics, and sperm production. Oestrogen is primarily produced by the ovaries in females. Androgen binding globulin is a protein that binds to testosterone in the bloodstream but is not produced by Leydig cells. Semen is produced by the accessory glands in the male reproductive system, not by Leydig cells. Therefore, the correct answer is C: Testosterone.

Correct Answer: C

Rationale: Step-by-step rationale: 1. Anorexia nervosa can affect both males and females. 2. Therefore, it is not exclusively in females. 3. Hypokalaemia, primary amenorrhea, and low FSH and LH are commonly associated with anorexia nervosa. 4. Choice C is incorrect as anorexia nervosa can affect individuals of any gender.

Correct Answer: B

Rationale: Step-by-step rationale for why answer B is correct: 1. Cushing's syndrome is characterized by excess cortisol production. 2. Women are more likely to develop Cushing's syndrome due to hormonal differences. 3. Women have higher cortisol levels naturally, making them more susceptible. 4. Men can still develop Cushing's syndrome but at a lower rate compared to women. Summary: A: Incorrect, as women are more likely to develop Cushing's syndrome. C: Incorrect, as the incidence is higher in women due to hormonal factors. D: Incorrect, as it refers to thyroid hormones, not cortisol in Cushing's syndrome.