male, 76 years, in general good health, active. Height 5'6", weight 69kgs. Medication after radioactive iodine treatment 4 yrs ago for hyperthyroidism, 125mcgms Thyroxine daily. Symptoms started 3 days ago, sudden overwhelming tiredness after mowing small lawn etc., progressing to heavy head, aching bones, low blood pressure (normally quite low anyway)feeling hot then cold and sweating lots. No fever. no runny nose or cough. No diarrhoea. Could this be a virus?