Hypothyroidism Support Group
Hypothyroidism is the disease state caused by insufficient production of thyrohormone by the thyroid gland. There are several distinct causes for chronic hypothyroidism, the most common being Hashimoto's thyroiditis and hypothyroidism following radioiodine therapy for hyperthyroidism. Advanced hypothyroidism may cause severe complications, the most serious one of which is...
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Your TPOab test probably had a greater than sign indicated as positive.
Here's a little bit of info about diagnosing Hashi's:
http://www.ncbi.nlm.nih.gov/pubmed/1092711
For whatever it's worth, Hashi's is the most common cause of hypothyroidism. Other possible causes are RAI or surgical removal of the thyroid, the effects of certain meds/treatments or the very rare pituitary dysfunction.
http://www.mayoclinic.com/health/thyroid-disease/AN00806
Since your thyroid function labs were most definitely hypothyroid, it's clear you are dealing with thyroid disease. Having measurable TPOab's indicate that it's autoimmune.