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: 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: 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: 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: The correct answer is D: Fine hairs. In secondary hypothyroidism, the pituitary gland fails to produce enough thyroid-stimulating hormone (TSH), resulting in low thyroid hormone levels. Fine hairs (or hair thinning) is a symptom of hyperthyroidism, not hypothyroidism. Normal cholesterol levels (Choice A) are seen in secondary hypothyroidism due to decreased metabolic rate. Menorrhagia (Choice B) can occur due to hormonal imbalances caused by untreated hypothyroidism. Low TSH levels (Choice C) are a characteristic feature of secondary hypothyroidism as the pituitary gland is not producing enough TSH to stimulate the thyroid gland.

Correct Answer: A

Rationale: The correct answer is A because Klinefelter's syndrome is characterized by small, soft testes due to the presence of an extra X chromosome (47, XXY). This leads to hypogonadism and inadequate testosterone production, resulting in underdeveloped testes. Choice B (46, XO) is incorrect as it refers to Turner syndrome. Choice C (upper segment> lower segment) is unrelated to Klinefelter's syndrome. Choice D (Gynaecomastia) is a symptom of Klinefelter's syndrome but not the defining characteristic.

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: Rationale: 1. GnRH directly binds to pituitary receptors. 2. GnRH specifically targets gonadotroph cells to release LH and FSH. 3. CRH and ACTH are related to stress and adrenal function, not reproductive hormones. 4. Tremor is unrelated to pituitary hormone regulation. Summary: Gonadotrophin releasing hormone (GnRH) is the correct answer as it directly stimulates the release of LH and FSH from the pituitary gland. Other choices are incorrect as they are not involved in the regulation of reproductive hormones.