The thyroid gland produces a number of hormones involved in the normal metabolic function of the body. Hypothyroidism (underactive thyroid) is when the thyroid gland is not producing enough thyroxine (T4).

This condition is almost always successfully treated by taking daily hormone tablets to replace the thyroxine your body is not producing. The synthetic version of thyroxine is called levothyroxine (L-thyroxine) and is available in many strengths to ensure fine daily hormone control. 

Common signs of an underactive thyroid are tiredness, weight gain and feeling depressed.