I had thyroid surgery about 12 years ago, and I take Synthroid daily. I suffer from severe excessive sweating - my hair gets wet any time I am moving around. I am extremely embarrassed by this. Could it be caused by my thyroid?
The thyroid gland is important in controlling many different basic functions of the body. It would be important to know the reason for your surgery, and whether all, or only part, of your thyroid was removed. If the entire gland was removed, the Synthroid is acting as a complete replacement - "replacement therapy" - and is supplying your body with the needed hormone. On the other hand, if part of the gland was removed, say for a goiter or a nodule, you may be taking the Synthroid to keep the rest of the gland from overproducing hormone or to keep it from growing into another goiter - known as "suppression therapy".
Your body may have a very fine balance of how much thyroid hormone it needs. Just a little too much will put you in a hyperthyroid state. Sweating can be seen with hyperthyroidism, but is uncommon as a lone symptom without any of the other signs or symptoms of hyperthyroidism.
Also, sweating only in your hair is unusual, although thinning hair can be a feature of hyperthyroidism. If you are only sweating in the hair with really nothing else, and your thyroid function tests are normal, there must be another cause of the sweating.
Sweating localized to one particular part of the body, and not in response to hot temperatures or physical activity, can be caused by over-activity or stimulation of the autonomic nervous system (that part of your nervous system that unconsciously controls your skin and the sweating reflex).
If the sweating is localized to one part of the body only, such as the arm, surgery can be done to cut some of these small controlling nerves, to reduce the sweating reflex. Obviously that won't work if the sweating is in the hair on your head. Sometimes there are medications that can control this sweating reflex, and you should ask your doctor who oversees your thyroid condition about this possibility.