I too worried about that. I am 35 yof with a strong family hx of heart disease. My maternal grandfather died one day after his 34th birthday from a heart attack and grandma is 4 time (yes four) survivor of heart attacks. I told doc about my concern when he prescribed such a high dose (150 mcg), but for my age and overall health he was not concerned with that. He said it is still lower than what my total replacement dose will be.
So, here's the answer from the Physicians Desk Reference aka PDR 2001.
"Signs and symptoms of Overdosage: Excessive doses of Synthroid result in a hypermetabolic state indistinguishable from thyrotoxicosis of endogenous origin. Signs and symptoms of thyrotoxicosis include weight loss, increased appetite, palpitations, nervousness, diarrhea, abdominal cramps, sweating, tachycardia, increased pulse and blood pressure, cardiac arrhythmias, tremors, insomnia, heat intolerance, fever, and menstrual irregularities. Symptoms are not alway evident or may not appear until several days after ingestion."
I won't take up too much more space, but the PDR also says that "Synthroid should be used with caution in patients with cardiovascular disorders, including angina, coronary artery disease, and hypertension, and in the elderly who have a greater likelihood of occult cardiac disease."
I found my PDR last year on the clearance shelf of my local Borders for $10.
[This message has been edited by happy4us (edited 09-14-2003).]