Hormones play essential roles throughout a woman’s life — from the menstrual cycle and fertility to bone strength, metabolic health, cognition, and overall well-being. Yet many women (and even some clinicians) are unsure how these hormones change with age or what hormone replacement therapy (HRT) actually involves. This overview highlights the three key reproductive hormones, how they function, and what happens as levels naturally shift over time.
Progesterone
Progesterone is produced primarily by the ovaries and, to a lesser extent, by the adrenal glands. Ovarian production is cyclic and depends on ovulation; as ovulation becomes irregular in perimenopause and eventually ceases, progesterone levels naturally fall.¹ Progesterone plays key roles in preparing the uterine lining, supporting early pregnancy, regulating the menstrual cycle, and balancing estrogen activity.¹ When the ovaries stop producing sufficient progesterone, the adrenals cannot fully compensate, which may contribute to symptoms such as sleep disruption or cycle changes.
Estrogen
“Estrogen” is actually a group of three hormones, each with different strengths and functions:
- Estradiol (E2): The strongest and most active estrogen during reproductive years.
- Estrone (E1): Becomes the primary form after menopause, produced largely in body fat.
- Estriol (E3): A weaker estrogen, seen mostly during pregnancy.
These three forms differ in potency, tissue effects, and how they change with age.² As ovarian estradiol production declines in menopause, the body increasingly relies on estrone, which can influence everything from bone density to vaginal tissue health. Understanding these distinctions helps avoid misconceptions about what “estrogen therapy” truly means.
Testosterone in Women
Although commonly labeled a male hormone, testosterone is also produced in women by both the ovaries and the adrenal glands. It contributes to muscle integrity, bone health, energy levels, cognitive function, and sexual well-being.³ Research supports the importance of physiologic testosterone levels for mood and musculoskeletal strength, although no testosterone product is FDA-approved specifically for women.³ Decisions about use must therefore be individualized and provider-directed.
Replacement vs. Contraceptive Doses
A common misconception is that HRT uses the same types of hormones or doses found in birth control methods. In reality, hormonal contraceptives use higher doses of synthetic hormones to suppress ovulation and prevent pregnancy.⁴ In contrast, hormone replacement seeks to restore physiologic — not contraceptive — levels of hormones that naturally decline with age. The purpose, dosing, safety considerations, and monitoring protocols differ significantly.
Your Partner in Compounded Hormone Therapy
At SATCRx, we work closely with both patients and licensed providers. If you would like to learn more about hormone therapy options, we can help connect you with qualified practitioners and prepare customized prescriptions as directed by your provider.
References
¹ Cable, J. K., & Grider, M. H. (2023). Physiology, Progesterone. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK558960/
² Cleveland Clinic. (2022). Estrogen: Hormone, Function, Levels & Imbalances. https://my.clevelandclinic.org/health/body/22353-estrogen
³ Davis, S. R., & Wahlin-Jacobsen, S. (2015). Testosterone in women — the clinical significance. The Lancet Diabetes & Endocrinology, 3(12), 980–992. https://doi.org/10.1016/S2213-8587(15)00284-3
⁴ Harper-Harrison, G. (2024). Hormone Replacement Therapy. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK493191/