Also, do they say they are FREE T3 and FREE T4?
Hypothyroidism can have many causes
. Iodine deficiency and the autoimmune disease, Hashimoto's thyroiditis, are two of the primary ones with Hashi's by far the most prevalent.
Symptoms include fatigue and/or drowsiness, weight gain, depression, constipation, hair loss, joint pain, etc. You can google for a complete list. Of course, not everyone has all the symptoms.