J.P. is a 37-year-old office manager who presents to her nurse practitioner with a complaint of arthritis in her wrists and ankles. She has gained 20 pounds in the past 6 months, despite eating a balanced diet. Her exercise regimen has suffered due to muscle cramps and headaches. On examination, the nurse practitioner palpates pitting edema in the forearms and legs. Name and describe a diagnosis that fits this case. Name and describe a diagnostic test that confirms your theory.