Last week I saw a cardiologist for pains in my back and under the arm on my left side. I have no history of heart disease, never smoked and was never overweight. My primary care physician did a lipid panel, and it was normal. Because I complained of having no energy or stamina, he prescribed thyroxine 25mcg. Is this safe to take when my blood test was normal? The only medications I am taking are simvastatin and travatan for glaucoma. I am 75.