Sometime ago I was corresponding with a man who related to me that he was experiencing symptoms that were suspicious of being thyroid hormone related. His father had been diagnosed with thyroid disease years earlier, plus his Doctor, who referred him to an Endocrinologist, also felt that his symptoms needed further evaluation for possible thyroid involvement. He posed some questions to me in regard to his iodine intake and his blood lab tested levels of iodine came back slightly elevated. He also asked if his symptoms of swelling in different tissues of his body and exercise intolerance possibly were related to thyroid dysfunction.
Below was my general response to this man:
I don't often hear of people getting their iodine levels checked because iodine doesn't necessarily tell you anything about your thyroid function. Iodine can elevate in the body due to what is in your diet (high iodine foods like kelp etc...) or because of supplements you take that contain iodine. The real tests of thyroid function are the actual thyroid hormone levels; "T-4 and T-3" (free levels) and one called "TSH" which is a pituitary hormone but is sensitive in monitoring thyroid function.
In regard to high iodine content foods or supplements containing iodine, I would suggest not consuming these until after you are evaluated for thyroid function because iodine can work adversely in people with "autoimmune thyroid disease", which is the most common cause of thyroid hormone imbalances in most industrialized countries, which I will describe further below. Let me add however, that iodine is the treatment for hypothyroidism caused by iodine deficiency but this type is almost non-existent in industrialized countries. Use of iodized salt alone usually contains as much iodine as average, healthy people need for thyroid function.
Your symptoms of feeling flu-ish and swelling (edema) after hard physical activity could possibly be thyroid related. This is especially true if you have a parent or sibling who has thyroid disease because it runs highly in families. You are possibly experiencing symptoms from the onset of "autoimmune thyroid disease" as I mention above. This type potentially causes symptoms even before thyroid hormone levels become abnormal. It is diagnosed via "thyroid antibodies" tests. These are the "TPO", "TG" and sometimes the "TSI" antibody levels. If any of these came back positive, you have thyroid autoimmunity, meaning your own immune system is attacking your thyroid gland.
I'm glad to hear that you are going to an Endocrinologist because most are better specialized in diagnosing and treating thyroid disorders. The thyroid gland is part of the Endocrine System, meaning one of the glands that, supplies our bodies with needed hormones. An Endo or a Thyroid Specialist are two Doctors that I suggest to people needing thyroid evaluation or even an MD who is highly experienced in treating thyroid disorders and diseases.