Differential Diagnosis

The patient presents with fatigue, sweating, a recent menstrual period, and a positive urine pregnancy test. The physical exam reveals diffuse enlargement of the thyroid gland, and laboratory studies show a thyroid-stimulating hormone (TSH) level of zero. Based on these findings, the differential diagnosis can be organized into the following categories:

• Single Most Likely Diagnosis
  • Hyperthyroidism due to Graves' disease: The patient's symptoms of fatigue, sweating, and tachycardia (heart rate 104), along with the diffuse enlargement of the thyroid gland and a TSH level of zero, are highly suggestive of hyperthyroidism. The positive urine pregnancy test and the patient's age also support this diagnosis, as Graves' disease is more common in young women and can be exacerbated by pregnancy.
• Other Likely Diagnoses
  • Pregnancy-induced hyperthyroidism: The patient's positive urine pregnancy test and symptoms of hyperthyroidism could also be attributed to pregnancy-induced hyperthyroidism, which is a condition that occurs in some pregnant women, particularly in the first trimester.
  • Toxic multinodular goiter: Although less likely, toxic multinodular goiter is another possible cause of hyperthyroidism, which could present with similar symptoms and laboratory findings.
• Do Not Miss Diagnoses
  • Thyroid storm: Although the patient is not in acute distress, thyroid storm is a life-threatening condition that can occur in patients with untreated or undertreated hyperthyroidism. It is essential to consider this diagnosis and monitor the patient closely for signs of deterioration.
  • Preeclampsia: The patient's pregnancy and elevated blood pressure (128/82) raise the possibility of preeclampsia, a condition that can have serious consequences for both the mother and the fetus if left untreated.
• Rare Diagnoses
  • Trophpoblastic disease: This rare condition, which includes hydatidiform mole and choriocarcinoma, can cause hyperthyroidism due to the production of human chorionic gonadotropin (hCG), which stimulates the thyroid gland.
  • Struma ovarii: This rare ovarian tumor can produce thyroid hormones, leading to hyperthyroidism. However, it is unlikely in this case, given the patient's symptoms and laboratory findings.