Many symptoms of hypothyroidism can be caused by a low level of thyroxine. Basically, everything 'slows down' but not all symptoms develop in all cases. Symptoms that commonly occur include tiredness, weight gain, constipation, aches, feeling cold, dry skin, lifeless hair, fluid retention, mental slowing, and depression.
The most common cause is due to an 'autoimmune disease' called autoimmune thyroiditis. The immune system normally makes antibodies to attack bacteria, viruses, and other 'germs'. If you have an autoimmune disease, the immune system makes antibodies against certain tissues of your body. A low level of Thyroxine confirms hypothyroidism so your doctor is trying to increase the levels. Levothyroxine tablets replace the body's natural hormone, so side-effects are uncommon. This replaces the thyroxine which your thyroid gland is not making. Most people feel much better soon after starting treatment, but some foods rich in calcium or iron may interfere with the absorption of levothyroxine from the gut. I don�t know of any alternative therapies, but treatment of levothyroxine is usually for life, has the doctor mentioned this?