Chances are you've never heard of a drug called Armour Thyroid. However, if you suffer from a thyroid condition, chances are good you not only know about it, but have spent the last few months in a vain attempt to find it.

"I was told today that I would no longer be able to get my prescription of Armour Thyroid filled due to a shortage in the product," Catherine, of Farmersville, Texas, told "How can a company have a shortage of a product that millions of Americans depend on for their very lives? My mother passed away when I was 15 from an untreated thyroid problem. I myself have already had a heart attack due to complications from my thyroid.

"I am unable to take the synthetic thyroid meds, due to allergic reactions. I sit here now, looking at my own daughter and grieving the thought of not being alive to see her graduate, get married, have children, all due to the fact that I can't get my medication."

Catherine, and hundreds more thyroid patients, have contacted since April, when the product began to fall into short supply. Many are distraught that the drug is not available, saying it has been the only thing that has helped their thyroid condition and allow them to live a normal life.

Armour Thyroid is a "natural" hormone replacement therapy because the thyroid glands are collected from pigs. The thyroids are processed, dried, powdered, and compounded to produce Armour Thyroid tablets.

Armour Thyroid is produced by a pharmaceutical firm called Forest Laboratories. In a statement on its Web site, the company has apologized for the supply interruption. It also has some good news.

"A supply of powdered Thyroid gland, the active ingredient of Armour Thyroid, has been made available to Forest by its supplier," the company said. "Forest has produced and shipped a limited supply of 1 grain, also known as 60 mg. We understand that this limited distribution will not meet the current anticipated demand for the product, and we continue to work diligently to meet demand. Although Forest is addressing the backlog of Armour Thyroid as quickly as possible, we are not prepared at this time to give a definitive date by which the product will be fully restocked."

Why the shortage?

The mystery remains about the reason for the sudden shortage. The Internet has been rife with rumors about possible causes - everything from the government diverting ingredients for swine flu vaccine to an FDA determined to phase out the drug.

The problem for many thyroid patients, they contend, is the synthetic replacement for Armour Thyroid not only doesn't work, but comes with nasty side effects.

"Throughout the years I've tried three different times to switch (to synthetics) and it made me feel so bad I'd rather go without anything than to use it and I take 180 mg/day," Susan, of Vallejo, Calif., told "My heart raced and my pounded, I had trouble swallowing and felt shaky to the point my hands would visibly shake and I couldn't concentrate. My hair was falling out to the point the shower drain would get clogged."