Measuring progesterone in the saliva is an alternative way of measuring the hormone. Progesterone measurement is used to confirm the occurrence of ovulation, assess infertility, monitor abnormal uterine bleeding (metrorrhagia), evaluate the health of the placenta in high-risk pregnancies, 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.
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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 occurs in the afternoon, around 6:00. In pregnant women, progesterone shows a similar rhythm during the second and third trimesters, with the lowest values 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 cycle's luteal phase 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 determines various functions necessary to maintain the pregnancy. In some infertile patients, ovulation may occur, but progesterone levels in the luteal phase are insufficient. Luteal phase deficiency results from inadequate production of progesterone by the corpus luteum. During menopause, the production of progesterone by the ovaries decreases, resulting in postmenopausal hormone levels in women are similar to those seen in men.
In addition to its role as a sex hormone, progesterone is a precursor to many other steroid hormones and cortisone. It 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.
Only 1 to 15% of progesterone in the blood is unbound or biologically active. The remaining progesterone binds to serum proteins. Unbound progesterone enters saliva through specific 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 sample collection is non-invasive and easy, without the possible complications and inconvenience of blood sampling, while ensuring the sensitivity and accuracy of the measurements.
