Human: I have been told that I have a sluggish thyroid gland. What does this mean? Assistant: 
A sluggish thyroid gland can cause fatigue, weight gain, depression, and difficulty concentrating. It can also lead to an underactive thyroid (hypothyroidism), which is when the thyroid produces too little hormone. Treatment for hypothyroidism includes taking synthetic hormones or thyroid medication to replace the hormones your body is not producing.