With age the natural process is declining levels of testosterone which gives a man his sexual desire. Besides you have thyroid and are on a pretty high dose of thyroxine. The potential causes of erectile dysfunction are many and vary widely from heart disease to emotional disorders, but researchers are finding that one common cause is often overlooked. There seems to be strong connection between various thyroid disorders and erectile dysfunction. Since thyroid disease can affect as many as one in ten men over the age of 50, this may mean that many of those dealing with erectile dysfunction and its related problems may have a reasonably simple disease to treat. The thyroid is a small gland located near the bottom of the neck. And while it is tiny, it secretes various hormones that have some level of control over many organs of the body. Two of the most common thyroid disorders found in men are hyperthyroidism, or when the thyroid is over productive, and hypothyroidism, when the thyroid is under productive. Both conditions may have some connection to erectile dysfunction. “Erectile dysfunction is a frequent finding in patients affected by thyroid disease, be it patients with hypothyroidism or hyperthyroidism. Please consult a competent experienced sexologist and seek advice and treatment. Good luck to you sir.