Saliva testing is a common way to assess hormone status, and is actually more accurate than testing hormone in the blood. It is the preferred way to assess hormone balance according to the World Health Organization. The reason for testing hormones in saliva is because hormones are normally bound to a protein in the blood–sex hormone binding globulin– and so is usually dissolved in the fatty part of the blood or attached to the cells in the blood. So when the blood is drawn it is then spun down to separate the red cells from the watery part of the blood (the serum), and the fatty part gets separated in another layer too. Any amount the is still in the serum is ready to be filtered by the kidneys and removed in the urine. Now saliva is a very interesting substance. You may think that it is watery and so hormones should not be present in it. However, saliva is a muco-polysaccharide and therefore hormones that are fat soluble are present in the saliva. The levels of hormone can vary depending on the time of the day that the saliva is tested and also on the time of the day that someone is using hormone therapy. So labs that average out the amount of hormones in the saliva over time (for example, over several samples) are going to give a more accurate assessment of the true hormone level. Frequently estradiol, progesterone, testosterone, DHEA, and cortisol levels can easily be tested this way. It certainly makes a lot more sense than to assess hormones in the blood. What I have found in my own practice is that people need far less hormones than what have been typically given people for treatment of hot flashes and night sweats–all the usual menopausal symptoms. And, what I have found out is that many people do not even need supplemental estrogen as their bodies are manufacturing enough of it on their own with conversion of hormone precursors (specifically DHEA) into estrogen and testosterone. You can listen to an interview I did with Dr. Mead on saliva testing for hormones at the following link: A Doctor’s Guide to Hormone Balance Part I.
In addition, saliva testing is now being done to assess how addicted a person who smokes is to nicotine. Apparently, the success of quitting can be predicted bases on whether a person is either lightly or heavily dependent on nicotine. What the saliva test does is assess 2 of the metabolites of nicotine, to determine how fast someone metabolizes the nicotine. Someone who metabolizes it more slowly may smoke less and therefore may find quitting easier than someone who metabolizes it faster and therefore smokes more in order to keep his or her nicotine at a certain level. These individuals may have a harder time quitting smoking or may need more than just simple measures to help them quit.