A 40-year-old woman presents with fatigability, weakness, lethargy, and poor concentration for 10 months. She gained 9 kg (19.8 lbs) of weight in the last six months. Her periods are irregular, occurring only six times in the last 10 months. Her most recent period was six weeks ago. Her menstrual cycles were regular before this. Her medical and surgical histories are unremarkable. However, she has not undergone routine health screening for the last five years. She is not on any medications, including over-the-counter drugs or supplements. Her family history is unremarkable. There is no history of allergies. A urine pregnancy test is negative. A complete blood count is normal. HbA1c is 6.4% (normal: <5.7%; prediabetes: 5.7-6.4%; diabetes: ≥6.5%).