Aromatase is an enzyme involved in the body’s hormone regulation. It acts as a biological catalyst, impacting various physiological processes. Aromatase activity is important for the production of certain hormones, contributing to overall bodily function.
What is Aromatase
Aromatase is an enzyme classified within the cytochrome P450 superfamily, specifically known as CYP19A1. It is a monooxygenase, meaning it incorporates one atom of molecular oxygen into its substrate. Localized within the endoplasmic reticulum of cells, it carries out its enzymatic functions there. Aromatase is also called estrogen synthetase or estrogen synthase, highlighting its primary role in estrogen biosynthesis. It is involved in the final steps of creating estrogens, a class of steroid hormones.
How Aromatase Functions
The primary function of aromatase is to convert androgens (often called male hormones) into estrogens (female hormones). This biochemical process is known as aromatization. Aromatase specifically converts androstenedione into estrone and testosterone into estradiol. This transformation is a key step in steroidogenesis, the pathway for synthesizing steroid hormones.
Where Aromatase is Active
Aromatase is found in various tissues throughout the body, allowing for localized estrogen production beyond the primary hormone-producing glands. In females, it is present in the ovaries, where it is involved in the menstrual cycle. In males, aromatase is active in the testes.
Beyond the gonads, aromatase is also expressed in numerous extragonadal sites. These include adipose (fat) tissue, where it can be a source of estrogen, especially after menopause. The enzyme is also found in the brain, bone, skin, blood vessels, and placenta. Its widespread presence allows for local estrogen production, influencing diverse tissue functions.
Aromatase’s Role in Health
Aromatase plays a role in various physiological functions through its production of estrogens. In female reproductive health, estrogen synthesis in the ovaries is important for regulating the menstrual cycle and supporting follicle development. In males, localized estrogen production in the testes is important for sperm development and function.
Estrogens generated by aromatase contribute to bone health in both sexes by influencing bone density. The enzyme’s activity in the brain contributes to neuroprotection and neuroendocrine function. Estrogens also have effects on the cardiovascular system and immune regulation. Aromatase’s presence in multiple tissues ensures estrogens support these diverse bodily systems.
Aromatase Imbalances and Medical Interventions
Disruptions in aromatase activity can lead to various health concerns due to altered estrogen levels. Excessively high aromatase activity can result in estrogen overproduction. In males, this can lead to gynecomastia, the enlargement of breast tissue. In both sexes, elevated estrogen levels can impact bone growth, potentially leading to short stature due to early epiphyseal closure.
High aromatase activity is also relevant in certain hormone-sensitive cancers, such as estrogen receptor-positive breast cancer. Here, cancer cells rely on estrogen for growth, and aromatase within the tumor can produce it. Medical interventions often target aromatase to manage these conditions.
Aromatase inhibitors (AIs) are a class of drugs designed to block the enzyme’s activity, thereby reducing estrogen production. These inhibitors work by either irreversibly binding to the enzyme (e.g., exemestane) or by reversibly competing for its binding site (e.g., anastrozole and letrozole). By lowering estrogen levels, especially in postmenopausal women where peripheral aromatase is a primary estrogen source, AIs can slow or stop the growth of hormone-sensitive breast tumors. AIs are commonly used as a treatment for breast cancer, often prescribed for several years to reduce recurrence risk. They may also be used to manage gynecomastia in some cases.