A 36-year-old woman comes to the office due to a 3-month history of palpitations and restlessness. In addition, she has had irregular menstrual periods for the last 6 months, and her last menstrual period was 45 days ago. The patient has a normal appetite and has had no weight change, headaches, swelling, shortness of breath, diaphoresis, or muscle weakness. She takes no prescription medications, and medical history is notable only for laparoscopic excision of a benign ovarian cyst at age 28. Family history is unremarkable. She works as a laboratory technician at a community hospital and does not use tobacco, alcohol, or illicit drugs. The patient is single and not sexually active. Temperature is 36.1 C (97 F), blood pressure is 140/70 mm Hg, pulse is 100/min, and respirations are 22/min. Pupils are normal and reactive to light with intact extraocular movements, no proptosis, and mild lid lag. The thyroid is easily palpable, nontender, and has no nodules. The extremities are warm to the touch and there is a slight tremor in the outstretched hands. Laboratory results are as follows: Which of the following is the most likely cause of this patient's thyroid abnormalities?

Question

A 36-year-old woman comes to the office due to a 3-month history of palpitations and restlessness.  In addition, she has had irregular menstrual periods for the last 6 months, and her last menstrual period was 45 days ago.  The patient has a normal appetite and has had no weight change, headaches, swelling, shortness of breath, diaphoresis, or muscle weakness.  She takes no prescription medications, and medical history is notable only for laparoscopic excision of a benign ovarian cyst at age 28.  Family history is unremarkable.  She works as a laboratory technician at a community hospital and does not use tobacco, alcohol, or illicit drugs.  The patient is single and not sexually active.  Temperature is 36.1 C (97 F), blood pressure is 140/70 mm Hg, pulse is 100/min, and respirations are 22/min.  Pupils are normal and reactive to light with intact extraocular movements, no proptosis, and mild lid lag.  The thyroid is easily palpable, nontender, and has no nodules.  The extremities are warm to the touch and there is a slight tremor in the outstretched hands.  Laboratory results are as follows:  Which of the following is the most likely cause of this patient's thyroid abnormalities?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c13a_338b_8f63_f78b00ad2a02_MD0005_00 This patient has symptomatic thyrotoxicosis and an elevated TSH consistent with central hyperthyroidism, most likely due to a TSH-secreting pituitary adenoma. In addition to TSH, these tumors may also secrete the biologically inactive alpha subunit and other pituitary hormones (eg, growth hormone leading to acromegaly). Serum T3 and T4 levels are elevated, which will lead to increased production of sex hormone-binding globulin by the liver. A diffuse goiter may be present, and patients may have local mass effect symptoms (eg, headache, visual field defects) but they do not have the extrathyroidal manifestations of Graves disease. Patients with thyroid hormone resistance syndrome due to mutations in the thyroid hormone receptor beta gene will also have an elevated TSH, increased levels of thyroid hormones, and a diffuse goiter. However, levels of alpha subunit and other pituitary hormones are not increased and sex hormone-binding globulin level is normal (as hepatic tissue is resistant to the increased thyroid hormone levels) (Choice C). In addition, administration of exogenous thyroxine will suppress TSH secretion in resistance to thyroid hormone, but TSH secretion from pituitary adenomas is not suppressible. There is also a commercial assay available for thyroid hormone receptor beta gene mutations that can further clarify the distinction. (Choices B and D) Pregnancy and other hyperestrogenic states can raise serum levels of thyroxine-binding globulin. Total T3 and T4 levels will be elevated but TSH is normal or low, and patients are clinically euthyroid. (Choice E) Thyrotoxicosis due to surreptitious thyroid hormone use will result in suppressed TSH levels. Educational objective: TSH-secreting pituitary adenomas cause central hyperthyroidism with elevated TSH and thyroid hormone levels. These tumors may also secrete the biologically inactive alpha subunit and other pituitary hormones and can cause mass effect symptoms (eg, headache, visual field defects). References: 2013 European thyroid association guidelines for the diagnosis and treatment of thyrotropin-secreting pituitary tumors. (http://www.ncbi.nlm.nih.gov/pubmed/24783044)

A 36-Year-Old Woman Comes to the Office Due to a 3-Month