Because hypothyroidism means your body isn't getting enough of the hormones it needs, the treatment involves a synthetic hormone to get your body chemistry back to normal. Symptoms subside soon after treatment starts, but most people with hypothyroidism need to stay on lifelong treatment. Due to normal fluctuations in hormone levels, doctors often need to adjust the level of hormone that patients receive. This constant rebalancing means that people with underactive thyroids and their physicians must always monitor the disease and effects of treatment.