Wednesday, July 22, 2009

Hormones 101

Until Cloud pointed it out in the comments to Free Range Kids Book Review, I hadn't realized that some hormones are proteins*.

From Medterms
Hormone: A chemical substance produced in the body that controls and regulates the activity of certain cells or organs.
The definition does not impose any limitations upon the type of molecule. They are defined only by their actions and their origin. I suspect that I am not the only one who thought that hormones were limited to smaller molecules like testosterone, progesterone and estrogen. They were the only ones pictured in my organic chemistry textbook. Birth control pills, for example, are typically a mixture of progesterone and estrogen. Ingest those, and they enter the bloodstream.

Protein or peptide hormones, in contrast, do not survive the digestive system. Protein hormones are made up of long chains of amino acids, several orders of magnitude larger than estrogen molecules. If we ingest them, they are digested into their constituent amino acids, which are absorbed into the blood stream. Protein hormones must be delivered by injection (shots) or infusion (IV).

Bovine Growth Hormone, bGH, is one of those protein hormones. It is injected into dairy cows. Though their use can measurable elevate levels of hormones in milk, they aren't likely to have an effect on humans with a healthy gut.

I do worry about its effect on the cows, though. There are some studies that show cows injected with bGH develop mastitis more frequently. Many mothers who nursed, myself included, can attest to the pain of mastitis. Mastitis is treated with antibiotics, which contribute to antibiotic resistance and are also excreted into the milk and the environment through their excrement...

I found this extraordinarily complete and unbiased Fact Sheet, Consumer Concerns About Hormones in Food, from researchers at Cornell. See their list of Fact Sheets regarding Chemicals in Food and Water.

* I never took biochemistry; organic chemistry passed in a blur as I dealt with health problems associated with organic chemistry lab (without fume hoods!) and my genetic susceptibility.

1 comment:

  1. Its funny what we take for granted. It didn't really occur to me that some people might not know that growth hormone is a protein.

    No wonder we have such a hard time with science-related policy in this country. We're pretty bad at communicating the relevant information to the public.

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