Thyroid hormone synthesis — MCQs

A patient with Graves' disease is treated with thiocyanate (a historical antithyroid agent). Thiocyanate helps reduce thyroid hormone production by:

A 49-year-old woman presents to the office because of tremors for 2 months. She says that her hands have been shaking a lot, especially when she feels stressed. In addition, she has been sweating more than usual and has lost 8 kg (17.6 lb) in the last 2 months. She has a past medical history of vitiligo. Her vital signs are a heart rate of 98/min, a respiratory rate of 14/min, a temperature of 37.6°C (99.7°F), and a blood pressure of 115/75 mm Hg. Physical examination shows a fine, bilateral hand tremor and a diffuse goiter. Which of the following hormonal imbalances is most likely present?

A 31-year-old woman presents to her primary care physician with a 2-week history of diarrhea. She says that she has also noticed that she is losing weight, which makes her feel anxious since she has relatives who have suffered from anorexia. Finally, she says that she is worried she has a fever because she feels warm and has been sweating profusely. On physical examination she is found to have proptosis, fine tremor of her hands, and symmetrical, non-tender thyroid enlargement. Which of the following types of enzymes is targeted by a treatment for this disease?

A 41-year-old woman comes to the physician because of a 3-month history of anxiety, difficulty falling asleep, heat intolerance, and a 6-kg (13.2-lb) weight loss. The patient's nephew, who is studying medicine, mentioned that her symptoms might be caused by a condition that is due to somatic activating mutations of the genes for the TSH receptor. Examination shows warm, moist skin and a 2-cm, nontender, subcutaneous mass on the anterior neck. Which of the following additional findings should most raise concern for a different underlying etiology of her symptoms?

A 27-year-old woman presents to her doctor complaining of pain in her neck that radiates to her left ear. The pain has been more or less constant for the last 3 weeks and increases when she chews and swallows. She was in her normal state of health before the pain started. She also mentions that she has been experiencing palpitations, muscle weakness, and increased sweating for the last 2 weeks. Past medical history is significant for a flu-like illness 2 months ago. She currently takes no medication and neither consumes alcohol nor smokes cigarettes. Her pulse is 104/min and irregular with a blood pressure of 140/80 mm Hg. On examination, the physician notices that the patient is restless. There is a presence of fine tremors in both hands. The anterior neck is swollen, warm to the touch, and markedly tender on palpation. Thyroid function tests and a biopsy are ordered. Which of the following deviations from the normal is expected to be seen in her thyroid function tests?

A 52-year-old male presents to clinic with complaints of anxiety and fatigue for 4 months. He has also been experiencing palpitations, muscle weakness, increased sweating, and an increase in the frequency of defecation. Past medical history is insignificant. He neither consumes alcohol nor smokes cigarettes. His pulse is 104/min and irregular, blood pressure is 140/80 mm Hg. On examination, you notice that he has bilateral exophthalmos. There are fine tremors in both hands. Which of the following results would you expect to see on a thyroid panel?

A previously healthy 27-year-old man comes to the physician because of a 3-week history of anxiety, diarrhea, and a 4.1-kg (9-lb) weight loss. On questioning, he also reports that he noticed a painless mass on his left testicle 2 weeks ago. His pulse is 110/min and irregular and blood pressure is 150/70 mm Hg. Examination shows diaphoresis and a fine tremor of the outstretched fingers. Testicular examination shows a 3-cm, firm, nontender mass on the left scrotum that does not transilluminate. This patient's underlying condition is most likely to be associated with which of the following findings?

An 18-year-old girl comes to the clinic because she is concerned about her weight. She states that she is on her school’s cheerleading team and is upset because she feels she is the “fattest” girl on the team despite her healthy diet. She says that in the last 2 weeks since practice began, she has lost 2 lbs. The patient has bipolar disorder I. Her medications include lithium and a combined oral contraceptive that was recently started by her gynecologist, because “everyone is on it." Her mother has hypothyroidism and is treated with levothyroxine. The patient’s BMI is 23.2 kg/m2. Thyroid function labs are drawn and shown below: Thyroid-stimulating hormone (TSH): 4.0 mIU/L Serum thyroxine (T4): 18 ug/dL Free thyroxine (Free T4): 1.4 ng/dl (normal range: 0.7-1.9 ng/dL) Serum triiodothyronine (T3): 210 ng/dL Free triiodothyronine (T3): 6.0 pg/mL (normal range: 3.0-7.0 pg/mL) Which of the following is the most likely cause of the patient’s abnormal lab values?

A researcher is studying physiologic and hormonal changes that occur during pregnancy. Specifically, they examine the behavior of progesterone over the course of the menstrual cycle and find that it normally decreases over time; however, during pregnancy this decrease does not occur in the usual time frame. The researcher identifies a circulating factor that appears to be responsible for this difference in progesterone behavior. In order to further examine this factor, the researcher denatures the circulating factor and examines the sizes of its components on a western blot as compared to several other hormones. One of the bands the researcher identifies in this circulating factor is identical to that of another known hormone with which of the following sites of action?

A 43-year-old woman comes to the physician because of a 3-month history of tremor, diarrhea, and a 5-kg (11-lb) weight loss. Her pulse is 110/min. Examination shows protrusion of the eyeball when looking forward. A bruit is heard over the anterior neck on auscultation. Serum studies show autoantibodies to the thyroid-stimulating hormone receptor. The patient decides to undergo definitive treatment for her condition with a radioactive tracer. The success of this treatment directly depends on the activity of which of the following?