Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with your doctor.
Synthroid, as you know, is used to treat hypothyroidism, or low levels of thyroid hormone (which has several causes). Over-replacement, too much
synthroid that the body does not require, can cause symptoms of "hyperthyroidism", too much thryoid hormone. These symptoms may include, but are not limited to,
tremorEssential tremor
Familial tremor
Hand tremor
Tremor,
heatBabies and heat rashes
Heat emergencies
Heat rash
Infant heat rash
Tenosynovitis intoleranceCeliac disease - sprue
Gestational diabetes
Lactose intolerance, weight loss, diarrhea,
palpitationsHeart palpitations (a sensation that the heart is beating), fast beating heart, and others.
In order to determine whether the dose of synthroid is too high, a blood test to check the TSH level is needed. When the synthroid dose is too high, the TSH level is too low.
Hyperthyroidism, or excess thyroid hormone in the body, brought about by either too much synthroid or from disease that cause hyperthyroidism, can worsen the tremor of Parkinson's disease. It might make it faster or more severe. Too much synthroid/hyperthyroidism itself (in the absence of Parkinson's disease) can cause a tremor, it is usually higher in frequency (faster) that the tremor of parkinson's disease.
However, note that too little thyroid hormone can also make some of the symptoms of Parkinson's disease worse such as slow thinking, slow movement, and other symptoms. The optimal dose of synthroid, as determined by a physician, will provide enough thyroid hormone for the body to function properly but not too much that symptoms, including worsening of a parkinson's tremor, occur.
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.