Thyroid function testingDownloads

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 35-year-old woman presents to the clinic for a several-month history of heat intolerance. She lives in a small apartment with her husband and reports that she always feels hot and sweaty, even when their air conditioning is on high. On further questioning, she's also had a 4.5 kg (10 lb) unintentional weight loss. The vital signs include: heart rate 102/min and blood pressure 150/80 mm Hg. The physical exam is notable for warm and slightly moist skin. She also exhibits a fine tremor in her hands when her arms are outstretched. Which of the following laboratory values is most likely low in this patient?