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Biochemistry

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Enzymes

Question
68 out of 79
 

A 53-year-old man comes to the physician because of progressive weakness and weight loss over the past 2 months. He says that he also began noticing areas of his skin getting

darker. Laboratory studies show:

Na+ 130 mEq/L, Cl 95 mEq/L, K 6.5 , HCO3 = 20

TLC 5000, Eosinophils 9.5%, Basophils 0.5%
Which of the following is the most likely diagnosis?



A Addison's disease

B Conn's syndrome

C Cushing's disease

D Cushing's syndrome

Ans. A Addison's disease

a. This patient most likely has Addison's disease, which is primary adrenocortical deficiency. It is a rare disease that is caused by a progressive destruction of the adrenal glands, usually due to idiopathic atrophy, surgery, infection, or hemorrhage.

b. Tuberculosis of adrenals is an important cause in India. The clinical symptoms include weakness, weight loss, hyperpigmentation, nausea and vomiting, and hypotension.

c. Laboratory findings include hyponatremia (due to aldosterone deficiency), hyperkalemia, and normocytic anemia with eosinophilia and lymphocytosis. The diagnosis is made with the ACTH stimulation test. Cortisol and aldosterone levels do not increase when the ACTH is given.

d. The treatment is glucocorticoid and mineralocorticoid replacement. Conn's syndrome is primary aldosteronism due to an aldosterone-producing adenoma.

e. Symptoms include headaches and hypertension. Laboratory findings include hypokalemia and hypernatremia. Metabolic alkalosis is common.

f. Cushing's disease is caused by an ACTH-producing pituitary tumor that produces excess aldosterone and adrenal androgen secretion. The symptoms include weakness and fatigue, increased weight, osteoporosis, hypertension, striae, amenorrhea, edema, and impaired glucose tolerance. A high-dose dexamethasone suppression test, CT scans and MRIs are used to make the diagnosis. Treatment is surgery.

g. Cushing's syndrome is similar to Cushing's disease except that it is due to adrenal hyperplasia, an adrenal neoplasm or exogenous, iatrogenic causes.

Syndrome of inappropriate antidiuretic hormone secretion is characterized by hyponatremia, anorexia, nausea and concentrated urine. It is caused by head trauma, a tumor or infections. The treatment is fluid restriction.

h. Drugs causing SIADH include: carbamazepine, chlorpropamide and vincristine. Demeclocycline is the DOC.

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