Nokea
Which of the following is the most common cause of Cushing's disease?
- A. ACTH-producing pituitary adenoma
- B. Adrenocortical adenoma
- C. Ectopic ACTH secretion
- D. McCune-Albright syndrome
Correct Answer: A
Rationale: The most common cause of Cushing's disease is an ACTH-producing pituitary adenoma. In this condition, the pituitary gland produces excessive amounts of adrenocorticotropic hormone (ACTH), which stimulates the adrenal glands to produce high levels of cortisol. This leads to the signs and symptoms of Cushing's disease, such as weight gain, high blood pressure, and muscle weakness. Adrenocortical adenoma refers to a benign tumor of the adrenal cortex that can also cause Cushing's syndrome, but it is not as common as an ACTH-producing pituitary adenoma. Ectopic ACTH secretion occurs when a non-pituitary tumor produces ACTH, leading to Cushing's syndrome. McCune-Albright syndrome is a rare genetic disorder that can cause various endocrine abnormalities, but it is not a common cause of Cushing's disease.
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Oxytocin and antidiuretic hormone (ADH; vasopressin) are:
- A. complex steroids.
- B. synthesized and stored in the posterior pituitary.
- C. released from the anterior pituitary where blood is hypotonic.
- D. synthesized in the hypothalamus and released from the posterior pituitary.
Correct Answer: D
Rationale: Oxytocin and antidiuretic hormone (ADH; vasopressin) are both synthesized in the hypothalamus, specifically in the supraoptic and paraventricular nuclei. After synthesis, they are transported along axons to the posterior pituitary where they are stored until they are released into the bloodstream when needed. This is why they are released from the posterior pituitary, not the anterior pituitary. These hormones have different functions in the body, with oxytocin being involved in labor and breastfeeding, while ADH plays a role in regulating water balance and blood pressure.
Commonest cause of 'ambiguous genitalia' in newborn is:
- A. Congenital adrenal hyperplasia
- B. True hermaphroditism
- C. Testicular ferminisation syndrome
- D. Pseudo-hermaphroditism
Correct Answer: A
Rationale: Congenital adrenal hyperplasia (CAH) is the most common cause of ambiguous genitalia in newborns. This condition is due to a deficiency of enzymes in the adrenal gland that are necessary for the production of cortisol. As a result, the body produces excess androgens (masculinizing hormones), leading to abnormal genital development in females. The external genitalia may appear ambiguous, with features of both male and female genitalia. This condition can be detected through newborn screening and confirmed through further hormonal and genetic testing. Treatment involves hormone replacement therapy to normalize hormone levels and surgery may be required to reconstruct the genitalia.
All of the following are featured by dermal hyperpigmentation except:
- A. Conn's syndrome
- B. Bronchogenic carcinoma
- C. Addison's disease
- D. Haemochromatosis
Correct Answer: A
Rationale: Dermal hyperpigmentation, also known as hyperpigmentation of the skin, is commonly associated with conditions such as Addison's disease, hemochromatosis, and bronchogenic carcinoma. In Addison's disease, there is increased production of melanin due to elevated levels of adrenocorticotropic hormone (ACTH) which stimulates melanocytes. Hemochromatosis can cause hyperpigmentation due to excess iron deposits in the skin. Bronchogenic carcinoma can lead to a condition known as acanthosis nigricans, characterized by dark, velvety discoloration of the skin primarily around the neck and armpits. However, Conn's syndrome, which is a primary aldosteronism resulting from an adrenal adenoma or hyperplasia, is not typically associated with dermal hyperpigmentation.
Which of the following is the underlying problem in neurogenic diabetes insipidus?
- A. Overproduction of vasopressin (antidiuretic hormone)
- B. Lack of oxytocin
- C. Overproduction of oxytocin
- D. Overproduction of prolactin
Correct Answer: E
Rationale: Neurogenic diabetes insipidus is a condition characterized by a deficiency of vasopressin (antidiuretic hormone). Vasopressin is responsible for regulating the body's water balance by controlling the reabsorption of water in the kidneys. In neurogenic diabetes insipidus, there is a problem with either the production, release, or action of vasopressin, leading to excessive urination and thirst. This condition can be caused by damage to the hypothalamus or pituitary gland, which are involved in producing and releasing vasopressin. Symptoms of neurogenic diabetes insipidus include frequent urination, excessive thirst, and dehydration.
Persistent muscular weakness is characteristic of:
- A. Conn's syndrome
- B. Acromegaly
- C. Hyperparathyroidism
- D. Myxoedema
Correct Answer: D
Rationale: Persistent muscular weakness is characteristic of myxoedema, which is severe hypothyroidism. Myxoedema can lead to general weakness and fatigue, as thyroid hormones play a crucial role in controlling metabolism and energy production in the body. Other symptoms of myxoedema include cold intolerance, weight gain, dry skin, and hair loss. Conn's syndrome (hyperaldosteronism) is characterized by hypertension and low potassium levels, not persistent muscular weakness. Acromegaly is a condition resulting from excess growth hormone production, leading to enlarged body parts and metabolic changes but not specifically muscular weakness. Hyperparathyroidism is associated with high levels of parathyroid hormone, which can lead to bone weakening and calcium imbalance, but it is not typically a primary cause of muscular weakness.