Progesterone Therapy

Progesterone is one of the two primary female sex hormones, working in partnership with estrogen to regulate the menstrual cycle, support fertility, and maintain overall hormonal balance. It is produced chiefly by the corpus luteum — the structure the ovary forms after releasing an egg each month — with additional amounts made by the adrenal glands and, during pregnancy, by the placenta. Because the corpus luteum only forms after ovulation, a woman's progesterone supply is directly tied to whether and how well she is ovulating.

Although progesterone is best known for its role in pregnancy, its influence extends far beyond reproduction. Progesterone helps stabilize the lining of the uterus, balances the growth-promoting effects of estrogen, and exerts a distinctly calming influence on the brain and nervous system. One of its metabolites, allopregnanolone, acts on the same GABA receptors that many anti-anxiety and sleep medications target, which is why healthy progesterone levels are associated with restful sleep, steady mood, and a sense of calm.

The bioidentical progesterone Dr. Riegel prescribes is molecularly identical to the progesterone your body produces naturally. This is an important distinction: it is not the same as the synthetic progestins found in many conventional prescriptions, which have a different molecular structure and a different profile of effects. By using progesterone that matches your own physiology exactly, Dr. Riegel aims to restore balance in the most natural, well-tolerated way possible.

Because progesterone has such a wide-ranging influence on sleep, mood, and the menstrual cycle, a deficiency can produce symptoms that are easy to mistake for stress, anxiety disorders, or simply the pressures of a busy life. Many women live with these symptoms for years without realizing that a treatable hormonal imbalance is at the root.

Sleep disturbance is one of the most common and disruptive signs of low progesterone. Women frequently describe difficulty falling asleep, waking in the early hours of the morning and being unable to return to sleep, or sleep that simply is not restorative. Because progesterone supports the calming GABA system in the brain, its decline often removes a natural sedative the body has relied on for decades.

Anxiety, irritability, and a diminished ability to cope with stress are also hallmark symptoms. Many women notice that they feel more "wired," more easily overwhelmed, or more prone to mood swings than they used to be — changes that often intensify in the second half of the menstrual cycle, when progesterone should normally be at its peak.

Changes in the menstrual cycle itself are another important clue. Low progesterone can cause periods to become heavier, more frequent, or unpredictable, and it commonly worsens premenstrual symptoms such as breast tenderness, bloating, water retention, and headaches. When progesterone falls while estrogen remains relatively high — a pattern sometimes described as estrogen dominance — these symptoms can become especially pronounced.

For most women, progesterone is the first hormone to decline on the road to menopause — often years before estrogen drops in any significant way. The reason lies in ovulation. As the ovaries age, ovulation becomes less frequent and less reliable. In any cycle where ovulation does not occur, no corpus luteum forms, and little or no progesterone is produced for that month. Estrogen, by contrast, can continue to be produced at relatively high and sometimes erratic levels well into perimenopause.

The result is a growing imbalance between the two hormones. Even before her periods become noticeably irregular, a woman may find that she is sleeping poorly, feeling anxious or on edge, experiencing heavier periods, or noticing that premenstrual symptoms she once managed easily have become far more intense. These are frequently the earliest signals of the hormonal transition — and they are precisely the symptoms that thoughtful progesterone replacement is designed to address.

This is where Dr. Riegel's career-long focus on hormonal medicine makes a meaningful difference. His approach begins with four years of hormone research at UT Southwestern Medical School and spans more than three decades of treating the full arc of a woman's hormonal life. He recognizes perimenopausal progesterone decline as a distinct, treatable stage rather than dismissing its symptoms as stress or the inevitable price of aging. By restoring progesterone to a healthy level, he helps many women regain the sleep, calm, and stability they had assumed were gone for good.

For women who use estrogen as part of hormone replacement therapy, progesterone plays a second, critically important role: protecting the lining of the uterus. Estrogen stimulates the endometrium — the tissue that lines the uterus — to grow. Without something to balance that effect, unopposed estrogen can cause the lining to build up excessively, a condition called endometrial hyperplasia that can, over time, increase the risk of endometrial cancer.

Progesterone counteracts this by stabilizing and maturing the endometrial lining, keeping estrogen's growth-promoting effect in check. For this reason, established clinical guidance from organizations such as The Menopause Society (formerly the North American Menopause Society) and the American College of Obstetricians and Gynecologists (ACOG) holds that any woman with an intact uterus who takes systemic estrogen should also receive adequate progesterone or another progestogen to protect the endometrium. This is not an optional add-on — it is a fundamental safety component of well-designed hormone therapy.

Dr. Riegel builds this protection into every estrogen-based protocol for women who have a uterus, using bioidentical progesterone dosed appropriately for each patient. It is one of the many reasons that hormone therapy is best managed by a physician with deep, specialized expertise rather than assembled piecemeal — the hormones must be balanced together, not prescribed in isolation.

One of the most important — and least understood — distinctions in hormone therapy is the difference between bioidentical progesterone and synthetic progestins. Both are used to supply the "progesterone side" of hormone therapy, but they are not the same substance, and the difference matters.

Bioidentical progesterone is molecularly identical to the progesterone your ovaries produce. The micronized form used in modern therapy is derived from plant sources and processed so that the body recognizes and uses it exactly as it would its own hormone. Synthetic progestins, on the other hand, are laboratory-created molecules that are structurally different from human progesterone. They were designed to mimic some of progesterone's effects, but because their structure differs, they can interact with the body's receptors differently and carry a different profile of side effects.

Many women who did not tolerate older synthetic progestins well — reporting bloating, mood changes, or breast tenderness — find bioidentical progesterone considerably more comfortable. The Menopause Society's hormone therapy guidance specifically recognizes micronized progesterone as an appropriate option for endometrial protection, and it has become the preferred choice for many hormone specialists who prioritize using hormones that match the body's own chemistry. Dr. Riegel uses exclusively bioidentical progesterone as part of his broader philosophy of restoring hormones with molecules the body already knows.

Effective progesterone therapy is never a matter of a single standard dose. At The Riegel Center, it begins with comprehensive evaluation — a detailed review of your symptoms and history alongside laboratory testing that measures progesterone in the context of your other hormones, including estradiol, testosterone, thyroid hormones, and cortisol. Because progesterone works in balance with estrogen, understanding the ratio between them is often more informative than looking at any single number in isolation.

From that foundation, Dr. Riegel designs a personalized protocol using bioidentical progesterone at the dose and in the form best suited to your needs. Oral micronized progesterone is frequently taken at bedtime, both because its calming metabolite supports sleep and because that timing fits naturally into a woman's routine. In other situations, transdermal or other delivery methods may be more appropriate. Dr. Riegel favors delivery methods that allow the dose to be adjusted precisely as your body responds, because optimizing hormones is an iterative process of testing, listening to how you feel, and fine-tuning.

Ongoing monitoring is a defining feature of care at The Riegel Center. Follow-up testing and symptom review allow Dr. Riegel to confirm that your progesterone level is in the optimal range, that it is well balanced against your estrogen, and — for women with a uterus on estrogen therapy — that your endometrium is properly protected. Over more than thirty years and roughly forty proprietary bioidentical formulations, he has refined an approach built on precision, personalization, and attentive follow-through, so that your therapy continues to fit you as your body changes.