A 34-year-old, previously healthy woman comes to the office due to irregular menstruation and a 4.5 kg (10-lb) weight gain over the past 6 months.  The patient also reports muscle weakness causing difficulty climbing stairs or lifting her child.  Blood pressure is 152/86 mm Hg and pulse is 72/min.  BMI is 31 kg/m².  Physical examination shows excessive fat accumulation in the abdomen and supraclavicular area.  Sun-exposed areas and skin creases are hyperpigmented and there are wide striae over the abdomen.  Coarse hair is present on the face, chest, and abdomen.  Which of the following sets of laboratory findings are most likely to be seen in this patient?

A 28-year-old woman comes to the office due to unintentional weight loss, fatigue, and sweating.  The patient has no neck pain.  Two months before this visit, she delivered a healthy male baby without complications.  The patient has no chronic medical conditions and takes no medications.  Blood pressure is 140/70 mm Hg, pulse is 110/min, and respirations are 16/min.  Oxygen saturation is 98% on room air.  Neck examination shows mild, diffuse enlargement of the thyroid gland with no tenderness.  The remainder of the physical examination is normal.  Laboratory evaluation shows low serum TSH and elevated serum thyroxine (T4) and triiodothyronine (T3).  Thyroid ultrasound with Doppler flow reveals a mildly enlarged gland with decreased blood flow.  Which of the following is most likely responsible for this patient’s disorder?

A 45-year-old woman is evaluated 2 weeks after she fractured her left radius during a fall from standing height.  Two months previously, she passed a renal stone.  There is no family history of osteoporosis or hypercalcemia.  Physical examination is unremarkable.  Serum laboratory results are as follows:

Bone density testing performed using dual-energy x-ray absorptiometry reveals osteoporosis.  Which of the following is the major contributor to bone loss in this patient?

A 29-year-old woman comes to the office due to unintentional weight loss, fatigue, and sweating.  The patient has had no neck pain.  Two months ago, she delivered a healthy boy with no perinatal complications.  The patient does not breastfeed the infant.  She has no chronic medical conditions and takes no medications.  Blood pressure is 140/70 mm Hg, pulse is 110/min, and respirations are 16/min.  Oxygen saturation is 98% on room air.  Neck examination shows mild, diffuse enlargement of the thyroid gland with no tenderness.  The remainder of the physical examination, including pelvic examination, is normal.  Laboratory evaluation reveals low serum TSH, elevated serum thyroxine (T4), and elevated serum triiodothyronine (T3).  Thyrotropin receptor antibodies are negative.  Which of the following is the most likely cause of this patient’s symptoms?

A 52-year-old woman comes to the office due to fatigue for the last 2 weeks.  The patient was previously healthy, but over the past 3 months, she has had significant weight loss without changing her diet.  She also reports increased sweating, hand tremor, and decreased sleep.  Examination shows diffuse, nontender enlargement of the thyroid gland.  The eyeballs are protuberant.  The remainder of the examination is notable for 1+ pitting edema in the ankles.  Which of the following parameters is most likely to be decreased in this patient?

A 29-year-old woman comes to the office due to increased hair loss.  She delivered a healthy baby boy 8 months ago and has not felt the same since.  The patient has fatigue and decreased libido, and her menstrual cycles have not returned.  She has no prior medical problems and no drug allergies.  The patient takes a multivitamin and does not use tobacco, alcohol, or illicit drugs.  There is no significant family history.  Blood pressure is 110/70 mm Hg and pulse is 58/min.  Physical examination shows diffuse alopecia and thickened, brittle nails.  The thyroid is nontender.  Laboratory results show decreased serum TSH and free thyroxine (T4) levels.  Which of the following is the most likely diagnosis in this patient?

A 60-year-old man comes to the office due to persistent cough for the past several weeks.  He reports producing minimal sputum that recently has contained occasional specks of blood.  The patient also has anorexia and has lost 7 kg (15.4 lb) over the past 2 months.  He has no previous medical conditions and takes no medications.  The patient has smoked a pack of cigarettes daily for 40 years and drinks alcohol on social occasions.  Temperature is 37.1 C (98.7 F), blood pressure is 130/80 mm Hg, pulse is 72/min, and respirations are 16/min.  On physical examination, respirations are unlabored, and there are occasional wheezes on the left side.  The remainder of the examination shows no abnormalities.  A chest x-ray reveals a hilar mass with adenopathy on the left side.  Laboratory results demonstrate a decreased serum sodium level.  Which of the following additional laboratory abnormalities are most likely to be present in this patient?

A 45-year-old man comes to the emergency department after experiencing sudden-onset headache with brief loss of consciousness while working in his yard.  CT scan of the brain reveals blood in the basal cistern from a ruptured intracranial aneurysm.  The patient is hospitalized, and endovascular coiling of the aneurysm is performed.  Over the next several days, his symptoms gradually improve but the patient develops worsening hyponatremia.  Which of the following is the most likely cause of this patient’s hyponatremia?

A 37-year-old woman comes to the office due to a two-month history of abdominal pain, salt craving, and weight loss.  She also has dizziness on standing.  The patient has no chronic medical conditions and takes no medications.  She does not use tobacco, alcohol, or illicit drugs.  Her mother and sister have hypothyroidism.  Blood pressure is 100/70 mm Hg supine and 80/50 mm Hg standing.  Laboratory results are as follows:

Which of the following changes in circulating hormone levels are expected in this patient?

A 28-year-old woman, gravida 1 para 1, comes to the office for a follow-up appointment 4 months after giving birth to a healthy boy.  For the past 3 weeks the patient has had progressive fatigue associated with loss of interest in day-to-day activities, irritability, and poor concentration.  In the 2 weeks prior to the onset of fatigue, she experienced excessive sweating and palpitations.  Blood pressure is 140/74 mm Hg and pulse is 60/min.  The thyroid gland is firm, diffusely enlarged, and nontender.  Laboratory results show elevated serum TSH and low free T4.  Which of the following pathological processes is likely responsible for this patient’s condition?

A 35-year-old woman is evaluated for a 3-month history of appetite loss, fatigue, weight loss, and abdominal pain.  She has no chronic medical conditions and takes no medications.  While undergoing upper gastrointestinal endoscopy, the patient develops cardiovascular collapse and dies, despite aggressive resuscitative measures.  On autopsy, increased pigmentation is noted around the nipple areola and anal and vaginal mucous membranes.  Which of the following additional findings are most likely to be seen on autopsy?

A 3-month-old boy is brought to the office due to fussiness, poor weight gain, and polyuria.  Urine volume is 700-800 mL/day.  The patient’s maternal grandfather has polydipsia and polyuria.  Serum sodium is 151 mEq/L.  Genetic testing reveals a vasopressin-2 receptor mutation.  Which of the following additional findings is most likely to be seen in this patient?

A 58-year-old man comes to the office for evaluation of a thyroid nodule.  The patient first noticed a painless neck lump 2 months ago, which has progressively enlarged.  He has had no heat or cold intolerance, recent weight changes, or difficulty breathing or swallowing.  Medical history is notable for well-controlled hypertension.  The patient has no history of radiation exposure or family history of thyroid diseases.  Physical examination shows a firm, nontender nodule in the right thyroid lobe.  Serum TSH level is normal, and ultrasonography shows a 4-cm solid nodule in the right thyroid lobe.  Fine-needle aspiration biopsy shows a large number of follicular cells dispersed in clusters and microfollicles.  The patient undergoes right thyroid lobectomy.  Which of the following histologic findings would confirm a diagnosis of follicular thyroid carcinoma in this patient?

A 45-year-old man comes to the office due to a 6-month history of headache, sweating, and pain in his lower back, knees, and small joints of his hands.  The pain increases with physical activity.  He is unable to remove his wedding ring due to swollen fingers.  The patient has also experienced excessive urination and loss of libido.  Examination shows a prominent jaw and enlarged supraorbital ridges.  The patient’s hands are notably broad with thickened fingers.  Multiple skin tags are noted on the nape of the neck.  Laboratory evaluation reveals low serum testosterone levels.  Which of the following is the most likely underlying cause of this patient’s joint symptoms?

A 72-year-old man is hospitalized for cough, purulent sputum, and shortness of breath.  His medical conditions include type 2 diabetes and hypertension.  A chest x-ray reveals right lower lobe pneumonia, and treatment is started with supplemental oxygen and antibiotics.  While hospitalized, the patient develops persistent sinus tachycardia.  Thyroid function tests ordered during the subsequent work up reveal:

Which of the following is the primary contributor to the decreased total T3 level in this patient?

A newborn boy is found to have markedly elevated serum TSH and low thyroxine on routine screening.  Laboratory findings using a venous blood sample confirm the diagnosis.  The patient was born at 39 weeks gestation to a 34-year-old healthy woman, who had been taking prenatal vitamins regularly.  He has no symptoms or abnormal findings on clinical examination.  Imaging studies reveal an ectopic thyroid gland just below the tongue.  Which of the following is the most likely cause of this patient’s otherwise normal physical examination despite abnormal thyroid laboratory findings?

Fifty obese adults without diabetes mellitus are enrolled in a 10-week weight loss program.  The program includes a low-calorie diet and moderate-intensity exercise for at least 150 minutes per week.  The study subjects who are adherent to the regimen lose an average of 7 kg (15.5 lb) at the end of 10 weeks.  Venous blood samples to study biochemical changes induced by weight loss are taken at the start of the trial and at the 10-week follow-up visit.  Which of the following hormonal changes are likely to occur during the course of the study?

A 26-year-old woman comes to the clinic due to worsening generalized weakness, myalgias, and unintentional weight loss.  She has primary hypothyroidism for which she takes levothyroxine.  Blood pressure is 110/70 mm Hg supine and 90/60 mm Hg standing.  She appears mildly emaciated.  Cardiopulmonary examination reveals no abnormalities.  Laboratory studies show mild normochromic, normocytic anemia; eosinophil count of 15%; and serum glucose of 65 mg/dL.  Which of the following additional changes is most likely in this patient?

A 46-year-old woman comes to the office for follow-up.  Six months ago, the patient underwent total thyroidectomy followed by radioactive iodine ablation for invasive follicular thyroid cancer with distant metastasis.  After surgery, she was prescribed levothyroxine to prevent thyroid cancer regrowth.  Over the past 4 months, the patient has had a 4.5-kg (10 lb) unintentional weight loss despite having a normal appetite.  She also feels unusually hot and sweaty.  Temperature is 37 C (98.6 F), blood pressure is 150/70 mm Hg, pulse is 110/min, and respirations are 17/min.  Examination reveals a fine hand tremor and sweaty palms.  Serum thyroid function testing would most likely reveal which of the following?

A neonate is found to have increased TSH and low thyroxine (T4) on routine screening.  He was born by vaginal delivery to a 32-year-old woman at 39 weeks gestation.  Apgar scores were 8 and 9 at 1 and 5 minutes, respectively.  Physical examination reveals an enlarged thyroid gland in the normal position.  Neck ultrasound confirms thyroid enlargement.  Which of the following is the most likely cause of this patient’s findings?

A 50-year-old man is seen in the office for new-onset constipation.  Family history is unremarkable.  Vital signs are within normal limits.  Physical examination reveals normal findings.  Serum laboratory results are as follows:

Which of the following is the most likely mechanism causing this patient’s low serum phosphate?

A 34-year-old man comes to the office for a follow-up visit.  The patient has had type 1 diabetes since age 12 and is diligent in taking insulin to achieve good glycemic control.  Over the past few months, he has had more frequent episodes of hypoglycemia despite no changes in his treatment, diet, or physical activity, but the episodes have been associated with less severe hypoglycemic symptoms compared to prior episodes.  Physical examination is unremarkable.  Laboratory results show normal basic metabolic panel and serum TSH level.  Hemoglobin A1c is 7.0%.  Which of the following factors is primarily responsible for this patient’s increased frequency of hypoglycemia?

A newborn boy is found to have a serum TSH above and serum thyroxine below the normal range for his age.  The patient was born at 39 weeks gestation via spontaneous vaginal delivery.  His mother has no medical conditions.  On examination, the patient’s length and weight are normal, and he has no apparent congenital abnormalities.  Ultrasound of the neck shows a normal-sized thyroid gland in the appropriate location.  Which of the following is the most likely cause of this patient’s condition?

A 41-year-old man comes to the office due to a 4-month history of fatigue, headache, weight loss, sweating, and palpitations.  He is otherwise healthy and takes no medications.  He does not use tobacco, alcohol, or illicit drugs.  Physical examination reveals lid lag and a fine hand tremor.  Neck examination reveals mild, diffuse enlargement of the thyroid gland.  Laboratory results are as follows:

Which of the following is the most likely cause of this patient’s disorder?

A 25-year-old woman comes to the office due to a 2-week history of neck pain.  The patient had an upper respiratory infection a month ago, during which she experienced nasal congestion, rhinorrhea, and a cough productive of clear sputum; her respiratory symptoms lasted for 5 days and resolved spontaneously.  The patient then felt well until 2 weeks ago, when she developed pain in the anterior neck associated with mild fever, palpitations, and excessive sweating.  She is otherwise healthy and takes no medications.  Pulse is 110/min.  The thyroid gland is tender to palpation and diffusely enlarged.  Other findings include sweaty palms, fine hand tremor, and brisk deep tendon reflexes.  Laboratory studies show suppressed TSH and elevated free thyroxine levels.  Erythrocyte sedimentation rate is 70 mm/hr.  Which of the following additional findings is most likely to be present in this patient at this time?

A 46-year-old man develops episodes of “dizzy spells” accompanied by palpitations and sweating during exercise.  His symptoms improve after drinking orange juice or eating a protein bar.  The patient was diagnosed with type 2 diabetes 6 months ago and advised to lose weight with dietary modification and exercise.  Since then, he has been working out intensively and has lost 10 kg (22 lb).  Which of the following mechanisms is responsible for this patient’s symptoms when exercising?

A 1-week-old newborn is seen for abnormal thyroid function tests that were performed as part of routine screening.  Serum thyroxine (T4) was low and serum TSH was normal.  The patient was born by spontaneous vaginal delivery at 40 weeks of gestation to a 28-year-old primigravida.  During the pregnancy, the mother took acetaminophen intermittently for low back pain.  Examination of the newborn shows no abnormal findings.  Repeat thyroid function test results are as follows:

Which of the following is the most likely cause of the patient’s abnormal thyroid function tests?

A 38-year-old man comes to the office with headaches, loss of libido, and erectile dysfunction for the last 3 months.  The patient has no chronic medical conditions and takes no prescription or over-the-counter medications.  He does not use tobacco, alcohol, or illicit drugs.  Vital signs are normal.  The examination is notable for peripheral vision loss, bilateral gynecomastia, and soft testes without masses.  Laboratory evaluation shows normal serum prolactin, normal β-hCG, low serum LH, and low serum testosterone.  Which of the following is the most likely mechanism for this patient’s gynecomastia?

A 19-year-old woman comes to the office to discuss treatment options for seasonal sneezing, rhinorrhea, and nasal congestion.  She has had these symptoms for the past few springs and summers but is now willing to “try anything” to allow her to concentrate on her upcoming final exams.  The patient has no significant medical history, takes no medications, and has no drug allergies.  Vital signs are within normal limits and physical examination reveals mild bilateral pale and boggy nasal turbinates with copious clear mucus.  Fluticasone, an intranasal glucocorticoid, is prescribed.  Which of the following is the most likely mechanism of action of this drug?

A 2-year-old girl is being evaluated for bilateral leg pain and muscle weakness with associated growth delay.  She is able to sit but unable to stand or walk without support due to pain.  Physical examination shows patchy alopecia, frontal bossing, wrist widening, and lateral bowing of the tibia and fibula.  Skeletal imaging reveals generalized osteopenia with cupping and fraying at the metaphyseal ends of the long bones of the upper and lower extremities.  Further evaluation reveals a homozygous inactivating mutation in the gene encoding the vitamin D receptor.  A serum sample would most likely show which of the following findings?

A researcher is investigating factors affecting adrenal hormone synthesis and release.  An intact adrenal gland is obtained from a donor cadaver, and a histologic section through the entire gland is shown below.  Cells from a specific part of the gland, indicated by the arrow, are extracted for further analysis.