A 35-year-old woman presents with fatigue, weight gain, and cold intolerance. Laboratory tests reveal high TSH and low free T4 levels. What is the most likely diagnosis?

Correct Answer: A

Rationale: The correct answer is A: Hypothyroidism. The patient's symptoms of fatigue, weight gain, and cold intolerance are classic signs of hypothyroidism. Elevated TSH and low free T4 levels indicate primary hypothyroidism. TSH is high due to the pituitary gland trying to stimulate the thyroid gland to produce more thyroid hormones, but the thyroid gland is unable to do so. Hyperthyroidism (choice B) would present with opposite symptoms and lab values. Thyroiditis (choice C) typically presents with transient hyperthyroidism followed by hypothyroidism. Thyroid cancer (choice D) is less common and typically does not present with these typical hypothyroid symptoms and lab findings.

Correct Answer: A

Rationale: The most likely diagnosis for the 45-year-old woman with fatigue, pruritus, jaundice, elevated bilirubin and alkaline phosphatase levels, and dilated intrahepatic bile ducts is Primary Biliary Cirrhosis (PBC). PBC is an autoimmune liver disease that primarily affects middle-aged women, leading to bile duct destruction and liver damage. The elevated alkaline phosphatase levels and presence of pruritus are typical in PBC due to impaired bile flow. Imaging showing dilated intrahepatic bile ducts supports the diagnosis of PBC as it indicates bile duct damage. Summary of other choices: B: Primary sclerosing cholangitis typically presents with strictures and beading of bile ducts on imaging. C: Gallstones would typically present with a common bile duct obstruction and not dilated intrahepatic bile ducts. D: Pancreatic cancer would typically present with different imaging findings and symptoms such as

Correct Answer: B

Rationale: The most likely diagnosis is Celiac disease (Choice B) due to the patient's symptoms of abdominal pain, bloating, diarrhea, and improvement with fasting, which are consistent with malabsorption seen in Celiac disease. The history of iron deficiency anemia also supports this, as it is a common complication of Celiac disease due to impaired absorption of nutrients. Irritable bowel syndrome (Choice A) typically does not improve with fasting, lactose intolerance (Choice C) does not usually cause iron deficiency anemia, and Crohn's disease (Choice D) typically presents with more severe symptoms and different patterns of improvement.

Correct Answer: A

Rationale: The most likely diagnosis for a 60-year-old man with fatigue, polyuria, polydipsia, hyperglycemia, and ketonuria is Type 1 diabetes mellitus. The key clues are the presence of ketonuria, which indicates the body is breaking down fats for energy due to lack of insulin in Type 1 diabetes. Additionally, the acute onset of symptoms in an older individual suggests an autoimmune destruction of pancreatic beta cells seen in Type 1 diabetes. Type 2 diabetes is less likely due to the acute presentation and ketonuria. Diabetes insipidus presents with polyuria but not hyperglycemia or ketonuria. Hyperthyroidism typically presents with symptoms such as weight loss, tremors, and heat intolerance, not the classic symptoms seen in this case.

Correct Answer: A

Rationale: The most likely diagnosis is A: Primary biliary cirrhosis. This is supported by the patient's symptoms of fatigue, pruritus, jaundice, elevated bilirubin and alkaline phosphatase levels, and dilated intrahepatic bile ducts. Primary biliary cirrhosis is an autoimmune liver disease that primarily affects middle-aged women, leading to destruction of intrahejson hepatic bile ducts. The normal common bile duct rules out obstruction from gallstones or pancreatic cancer. Primary sclerosing cholangitis typically presents with strictures in the bile ducts, which is not seen in this case. Therefore, the combination of symptoms, lab findings, and imaging results point towards primary biliary cirrhosis as the most likely diagnosis.