Oestrogen is a category of steroid hormones that regulate bodily development and function. The three primary forms made by the body are estrone (E1), estradiol (E2), and estriol (E3). While most associated with females, oestrogen is also synthesized in males, where it circulates at lower levels but still performs important physiological roles.
Primary Functions of Oestrogen
Oestrogen directs significant aspects of female reproductive health, beginning with puberty. Rising levels prompt the development of secondary sexual characteristics, such as the growth of breasts and the widening of hips. This hormonal increase is responsible for the maturation of the uterus and the onset of the menstrual cycle.
During the first half of the cycle, known as the follicular phase, increasing oestrogen levels cause the lining of the uterus, the endometrium, to thicken in preparation for a potential pregnancy. This surge in oestrogen, primarily estradiol, also triggers the release of a luteinizing hormone, which is the signal for an ovary to release an egg during ovulation. Should pregnancy occur, the placenta produces high levels of oestriol to support the growing fetus and ready the body for lactation.
Beyond reproduction, oestrogen has systemic effects. It is a key regulator of bone metabolism, helping to maintain bone density by managing the cells that break down bone tissue. This hormone also contributes to cardiovascular health by managing cholesterol levels, often increasing high-density lipoproteins (HDL) while decreasing low-density lipoproteins (LDL). Oestrogen supports skin health by stimulating collagen production, which helps maintain skin’s elasticity and moisture.
In males, oestrogen also has defined roles, though it is present in smaller quantities. The predominant form in men, estradiol, is converted from testosterone. This hormone is important for modulating libido, supporting erectile function, and contributing to the maturation of sperm. A proper balance between testosterone and oestrogen is necessary for these functions.
Oestrogen Fluctuations Across a Lifetime
Oestrogen levels are not static; they change in predictable patterns throughout a person’s life, influencing physical and emotional states at each stage. After remaining low during childhood, levels surge at puberty, initiating the reproductive capabilities and physical changes associated with this transition. This marks the beginning of decades of cyclical hormonal fluctuations tied to the menstrual cycle.
During the reproductive years, oestrogen levels rise and fall monthly. Estradiol, the most potent oestrogen, peaks just before ovulation to facilitate the release of an egg. Following this peak, levels dip before rising again in the second half of the cycle. If pregnancy does not occur, oestrogen levels fall sharply, leading to menstruation.
Pregnancy introduces a dramatic and sustained shift in oestrogen production. The placenta takes over, producing vast amounts of estriol, which becomes the dominant oestrogen. These high levels are necessary to maintain the pregnancy, support fetal development, and prepare the mother’s body for childbirth and breastfeeding.
The final major fluctuation occurs during the transition to menopause, known as perimenopause. During this time, the ovaries’ production of oestrogen becomes erratic, leading to unpredictable swings in hormone levels. Eventually, production declines significantly, leading to menopause, which is confirmed after 12 consecutive months without a period. Post-menopause, estrone, a weaker oestrogen produced mainly by fat tissue, becomes the body’s primary form.
Symptoms of Oestrogen Imbalance
Deviations from the normal range of oestrogen can lead to a variety of symptoms, which differ depending on whether levels are too low or too high.
Low Oestrogen
Low oestrogen is most commonly associated with menopause but can occur at other times due to various health conditions. One of the most well-known symptoms is the onset of hot flashes and night sweats, caused by oestrogen’s influence on the hypothalamus, the brain’s temperature-regulating center. Another frequent symptom is vaginal dryness, where the tissues become thinner and less lubricated.
The effects of low oestrogen extend to mood and cognitive function. Many people experience mood swings, irritability, and an increased risk for anxiety or depression. Sleep disturbances, trouble concentrating, and fatigue are also common. Furthermore, low oestrogen can lead to physical changes like dry skin, thinning hair, and an increased risk of bone density loss.
High Oestrogen
When oestrogen levels are high relative to other hormones like progesterone, a state sometimes referred to as oestrogen dominance, a different set of symptoms can emerge. This can manifest as bloating and water retention, as well as breast tenderness and swelling. Menstrual patterns are often affected, leading to periods that are heavier or irregular.
Mood swings are also a feature of high oestrogen, similar to those experienced in severe premenstrual syndrome (PMS). Some individuals may experience headaches or migraines that are hormonally triggered. Consistently high oestrogen levels can be associated with the development of noncancerous uterine fibroids and breast lumps. This imbalance can occur if the body produces too much oestrogen or struggles to excrete it efficiently.
External Influences on Oestrogen Levels
Medical interventions are a common source of hormonal influence. Hormonal contraceptives, such as birth control pills, deliver synthetic forms of oestrogen and progestin to suppress ovulation and manage the menstrual cycle. Hormone Replacement Therapy (HRT) is often used during menopause to supplement the body’s declining oestrogen, helping to alleviate symptoms like hot flashes and prevent bone loss.
Diet can also play a role through compounds known as phytoestrogens, which are plant-derived substances that can mimic the body’s natural oestrogen. Foods like soy and flaxseed are rich in these compounds. The effects of phytoestrogens are complex, as their activity is much weaker than endogenous oestrogen, and their impact can vary between individuals.
Certain environmental chemicals, known as endocrine-disrupting chemicals (EDCs), can interfere with the body’s hormone system. These substances, found in some plastics like BPA, pesticides, and industrial products, can mimic oestrogen and interact with its receptors. This interference can disrupt normal hormonal signaling pathways, though the precise long-term health impact of low-level environmental exposure continues to be an area of active research.