Measuring progesterone in the saliva is used as an alternative way of measuring the hormone. Progesterone measurement is used to confirm the occurrence of ovulation, to assess infertility, to monitor abnormal uterine bleeding (metrorrhagia), to evaluate the health of the placenta in high-risk pregnancies, to determine the efficacy of progesterone injections that are given to women to support early pregnancy as well as to monitor certain patients with adrenal disorders.
Progesterone is a steroid hormone of great importance for ovulation, fertility, pregnancy, and menopause. The synthesis of progesterone takes place in the placenta, adrenal glands, and gonads. In normal non-pregnant women during the luteal phase of the menstrual cycle, progesterone exhibits a daily (circadian) rhythm of secretion. Its maximum secretion takes place in the afternoon around 6:00. In pregnant women, progesterone shows a similar rhythm during the second and third trimesters, with the lowest values being observed in the morning and the maximum in the late afternoon. In men, progesterone is thought to play a role in testicular physiology.
The primary function of progesterone during menstruation in women is to prepare the endometrium for implantation of the fertilized egg. Therefore, levels increase during the luteal phase of the cycle immediately after ovulation. If implantation does not occur, progesterone returns to follicular phase levels. If pregnancy occurs, progesterone continues to rise to very high levels and it determines a variety of functions that are necessary to maintain the pregnancy. In some infertile patients, ovulation may occur but progesterone levels in the luteal phase are insufficient. Luteal phase deficiency is the result of insufficient production of progesterone by the corpus luteum. During menopause, the production of progesterone by the ovaries decreases, with the result being that postmenopausal hormone levels in women are similar to those seen in men.
In addition to its role as a sex hormone, progesterone also serves as a precursor to many of the other steroid hormones and cortisone. Progesterone is also synthesized in the brain and nervous system, where it acts as a neurosteroid molecule that can affect the survival and growth of nerve cells and is involved in brain development. In addition to neuroprotection, progesterone plays a role in maintaining skin elasticity and the development of bone tissue. Progesterone also neutralizes the action of estrogens in the endometrium.
In the blood, only 1 to 15% of progesterone is in its unbound or biologically active form. The remaining progesterone binds to serum proteins. Unbound progesterone enters saliva through certain intracellular mechanisms. In saliva, most of the progesterone is not bound to proteins. The correlation between measured plasma progesterone and salivary progesterone levels is very high.
Measurements of hormones in saliva are an excellent choice, because the collection of the sample is non-invasive and easy, without the possible complications and inconvenience of blood sampling, while ensuring the sensitivity and accuracy of the measurements.