What of the following statements best describes a toxic thyroid adenoma?

Correct Answer: D

Rationale: Step 1: Toxic thyroid adenoma is characterized by a benign tumor in the thyroid gland. Step 2: This tumor produces excessive amounts of thyroid hormones, particularly T3 and T4. Step 3: The tumor arises from the follicular cells of the thyroid gland. Step 4: Choice D accurately describes a toxic thyroid adenoma as a benign tumor producing excessive thyroid hormones from follicular cells. Summary: Choice A is incorrect because it describes autoimmune thyroid disease, not a toxic adenoma. Choice B is incorrect as it describes a malignant tumor, not a benign one. Choice C is incorrect as it describes thyroiditis, not a toxic adenoma.

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: B

Rationale: Thyroid acropathy, also known as thyroid dermopathy, is a skin condition commonly associated with Graves' disease. This autoimmune disorder causes an overactive thyroid gland, leading to high levels of thyroid hormones in the blood. The excess thyroid hormones can trigger changes in the skin, resulting in thyroid acropathy. Subclinical hypothyroidism (choice A) is characterized by slightly elevated TSH levels with normal thyroid hormone levels, not typically associated with thyroid acropathy. Myxoedema (choice C) refers to severe hypothyroidism and is not linked to thyroid acropathy. Medullary carcinoma of the thyroid (choice D) is a type of thyroid cancer and is not known to cause thyroid acropathy. Therefore, the correct answer is B, Graves' disease, as it is the most common condition associated with thyroid acropathy.

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: B

Rationale: The correct answer is B: Kidney disease. Oral contraceptive pills are contraindicated in patients with kidney disease due to the risk of impaired drug clearance and potential adverse effects on renal function. Breast cancer (A), liver disease (C), and prior history of deep venous thrombosis (D) are all contraindications to the use of oral contraceptives due to increased risks of complications such as thrombosis or exacerbation of underlying conditions.

Correct Answer: D

Rationale: Step 1: Toxic thyroid adenoma is characterized by a benign tumor in the thyroid gland. Step 2: This tumor produces excessive amounts of thyroid hormones, particularly T3 and T4. Step 3: The tumor arises from the follicular cells of the thyroid gland. Step 4: Choice D accurately describes a toxic thyroid adenoma as a benign tumor producing excessive thyroid hormones from follicular cells. Summary: Choice A is incorrect because it describes autoimmune thyroid disease, not a toxic adenoma. Choice B is incorrect as it describes a malignant tumor, not a benign one. Choice C is incorrect as it describes thyroiditis, not a toxic adenoma.

Correct Answer: B

Rationale: The correct answer is B: ductless. Endocrine glands release hormones directly into the bloodstream without the use of ducts. This allows hormones to reach target organs throughout the body. Choice A (vascular) is incorrect because it refers to the presence of blood vessels, which is common in all glands, not just endocrine glands. Choice C (square) is irrelevant as the shape of glands does not determine their function. Choice D (autonomous) is incorrect as it does not accurately describe endocrine glands; while they function independently, the term "autonomous" does not specifically apply to them.

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: C

Rationale: Rationale for choice C (FSH) being correct: 1. FSH stimulates Sertoli cells in the testes. 2. Sertoli cells produce androgen binding globulin (ABG). 3. ABG binds to testosterone, regulating its availability. 4. FSH indirectly influences testosterone levels via ABG production. Summary of incorrect choices: A. LH stimulates Leydig cells to produce testosterone, not Sertoli cells. B. GnRH regulates the release of FSH and LH but does not directly stimulate ABG production. D. Oxytocin is not involved in the regulation of Sertoli cells or ABG production in males.