There are temporary types of thyroiditis including one called "Viral thyroiditis", which they also refer to as "DeQuervain's thyroiditis" and if it is painful, it may be referred to as "Sub-Acute thyroiditis". If it is not painful, they may call it "Silent Thyroiditis".

While many people who experience one of these temporary types, have no problems afterward, when it resolves within a few weeks, others who experience them, go on to develop autoimmune thyroiditis, also referred to as "Hashimoto's thyroiditis". This type is not temporary but usually requires lifelong treatment with thyroid hormone replacement medication. It is also the most common cause of hypothyroidism or low-functioning thyroid, in the USA and most other industrialized countries. I know people with these types can develop Hashimoto's because I have corresponded directly with people whom this has happened to and I have also seen this scenario attested to on thyroid disease forums.

It could also be that these patients already had the beginnings or early onset of Hashimoto's developing in their bodies when they contracted one of these other types of temporary thyroiditis and it hastended the onset of Hashimoto's.

A Doctor can diagnose Hashimoto's, through testing of the "thyroid antibodies". These are the killer cells from the immune system, that are sent to destroy the thyroid gland (they normally attack germs and allergens) . They refer to this as autoimmune disease, when the body turns on itself and attacks part of its own natural tissue. One theory is that the immune system recognizes a natural part of the body as an intruder because of a virus that has settled into these tissues and in order for the immune system to attempt fully eradicating the virus, it has to attack the tissue that contains or is holding the virus. Over time the immune system is successful in damaging and ultimately destroying the thyroid gland, which results in hypothyroidism, a low functioning thyroid gland.

The thyroid antibodies that cause autoimmune hypothyroidism (Hashimoto's), are the "anti-thyroidperoxidase" (TPO) and the "anti-thyroglobulin" (TG). If a person tests positive for either or both of these antibodies (also called "auto-antibodies"), through blood testing, this would confirm Hashimoto's Disease/thyroiditis as a cause of hypothyroidism. There is also a thyroid tissue biopsy that can be performed, called an FNA (Fine Needle Aspiration) and this is even more diagnostic of Hashimoto's but blood testing is a logical place to start.

Doctors, usually also test these patients for low thyroid hormone to see if hypothyroidism has already begun. A "thyroid Panel", that includes the "TSH" level and the "Free T-4" and possibly also the "Free T-3", can determine how far along in causing hypothyroidism, Hashimoto's is. Some patients have Hashimoto's but their thyroid hormones and TSH are in normal range and they will still experience a degree of symptoms, despite hypothyroidism not being evident on blood labs. This is confirmed in a number of medical research studies and not just my opinion. Some Doctors start these patients on a small dose of thyroid hormone replacement medication if thyroid autoimmunity is present, along with hypothyroid symptoms.

Doctors should order the TPO and TG antibodies blood tests, along with a thyroid panel when evaluating a patient suspected of having hypothyroid disease. If a Doctor is not willing to order these tests, I would find one who is willing. This statement comes from my own person experience with a Doctor not ordering proper blood tests for me, when I suffered depression, anxiety, joint aches, dry skin, fatigue etc..., and my thyroid disease only being diagnosed, once I demanded these blood tests. The Doctor was trying to convince me that my symptoms were all emotional or psychosomatic when I knew for a fact I had a physical, medical problem in need of being diagnosed. In my case, both my thyroid panel and antibodies tests were abnormal and thyroid hormone therapy was highly effective in relieving my symptoms.