What is the relationship between hormones and proteins?

Question

What is the relationship between hormones and proteins: are hormones a group of specific proteins (or vice versa)?

Or are there some hormones that are not considered proteins (or vice versa)?

Can hormones be found in plant food (similar to proteins)?

Answer 1

According to this book "Endocrinology: An integrated Approach", which is freely available via the NCBI Bookshelf (http://www.ncbi.nlm.nih.gov/books/NBK20/) in Chapter 1:

Hormones can be derived from amino acids. These are the protein or peptides hormones which are composed from a very small number of amino acids to more than 200. An example of those hormones would be insulin or the anterior pituitary hormones.

Hormones such as insulin, GH (growth hormones) and IGF-I (insuline like growth factor) play a major role in the regulation of protein metabolism 1.

Hormones can also derive from cholesterol (ex vitamin D, adrenal or gonadal hormones), from fatty acids/phospholipids (ex prostaglandin, prostacyclin), from tryptophan (ex melatonin, serotonin) or tyrosine (ex catecholamines such as norepinephrine or epinephrine)

Some decades ago, phytoestrogens have been increasingly described in plants. According to Patisaul et al: Phytoestrogens are naturally-occurring plant compounds that are structurally and/or functionally similar to mammalian estrogens and their active metabolites. In his paper, he describes the potential roles of these phytoestrogens 2

References

• Umpleby AM et al, The hormonal control of protein metabolism. Baillieres Clin Endocrinol Metab. 1996 Oct;10(4):551-70.
• Patisaul HB, Jefferson W. The pros and cons of phytoestrogens. Frontiers in neuroendocrinology. 2010;31(4):400-419. doi:10.1016/j.yfrne.2010.03.003.

Answer 2

A protein is a long folded chain of amino acids. A chain of two or more amino acids is called a peptide.

Now, hormones are grouped into three classes based on their structure:

• Peptides: like insulin
• Steroid (Lipids): derived from cholesterol, like sex hormones.
• Amines: derived from one amino acid (not peptide) like the thyroid hormones derived from tyrosin.

There are, actually plant hormones that stimulate growth in plants, like Auxins, Cytokinins, and Gibberellins.