They gain weight and cant lose it or they have trouble keeping it on. often cause a negative energy balance which results in weight loss. In addition, other conditions, such as fibromyalgia, occur commonly in peopl. Increased lupus activity can sometimes cause weight loss, and certain. Hypothyroidism can cause weight gain, fatigue, depression, moodiness, and dry hair and. The thyroid gland helps regulate the bodys metabolism and as such can. Hypothyroidism can cause mild weight gain or make it hard to lose. The thyroid gland controls the overall level of metabolism in the body. This weight gain does not usually coincide with an increased appetite in fact, it is usually. medication just replaces the hormone that has been lost.