Sally is a 40 year old lady who presents with a 4 month history of fatigue and irritability. She has noticed various joint pains and muscle cramps and thought this was just a normal part of ageing. There is no change in bowel habit, abdominal pain or bloating. She denies any urinary symptoms. Past medical history includes Coeliac disease which is well controlled.
Based on the history alone, what is her most likely diagnosis?
