It’s common for women to notice changes in their breast size and shape as they transition through menopause. One of the most noticeable changes for many women is an increase in breast size, often coupled with a feeling of fullness or heaviness in the breasts. What causes breasts to get bigger after menopause? Here’s a look at some of the key factors behind this change.
Hormonal Changes
Shifting hormone levels are the main driver of breast enlargement after menopause. During the years leading up to menopause, a woman’s ovaries gradually produce less of the hormones estrogen and progesterone. These hormonal changes cause menstrual cycles to become irregular and eventually stop completely. However, it takes time for the body’s hormone production to reach a new postmenopausal normal.
In the transition years around menopause, estrogen levels may spike and fall unevenly as the ovaries sputter. At the same time, the adrenal glands and other tissues continue producing some estrogen. These fluctuating and eventually declining estrogen levels lead breast tissue to become less dense and fattier. This change in breast composition often translates to an increase in breast size.
Lower Progesterone
Progesterone helps balance the effects of estrogen in breast tissue. Premenopausally, progesterone levels rise and fall cyclically along with estrogen during the menstrual cycle. After menopause, progesterone levels remain persistently lower since ovulation ends. The loss of progesterone’s counterbalancing effects allows estrogen to have a greater impact on breast tissue.
Higher Estradiol
Of the different forms of estrogen produced in the body, estradiol tends to predominate after menopause. Estradiol is the strongest estrogen and seems to have the greatest impact on breast tissue. Postmenopausal estrogen production relies more on the conversion of androgens like testosterone into estradiol by aromatase enzymes in fat tissue.
Lower Sex Hormone Binding Globulin
Sex hormone binding globulin (SHBG) is a protein made by the liver that binds to estrogen and testosterone in the bloodstream. When estrogen is bound to SHBG, its effects are muted. SHBG levels fall in perimenopause and after menopause. This means a higher proportion of estrogen floating around the body is free and biologically active rather than inertly bound to SHBG.
Breast Tissue Changes
The hormonal influences of menopause trigger changes in the cellular structure and composition of breast tissue that lead to enlargement:
- Greater fat content – Breast tissue becomes fattier and less dense.
- More fluid – Blood flow increases and more fluid accumulates in breast tissue.
- Lobule growth – Milk-producing lobules don’t shrink as much after menopause as they did after each menstrual cycle premenopause.
- Stretching ligaments – Supportive ligaments stretch from breast expansion.
Lower Collagen
Estrogen helps stimulate collagen production while progesterone inhibits it. The combined loss of estrogen and progesterone after menopause allows collagen breakdown to outpace collagen synthesis. With less collagen to provide structural support, breast tissues become lax and expanded.
Increased Prolactin
The hormone prolactin helps stimulate breast growth and milk production during pregnancy and nursing. Estrogen keeps prolactin in check premenopause. After menopause, prolactin levels are higher in relation to estrogen as a result of estrogen’s decline. Higher prolactin in the breast tissue environment prompts fluid and tissue accumulation.
Weight Gain
Gaining body fat is common during the menopause transition for a few reasons:
- Slower metabolism from aging and lower estrogen.
- Loss of muscle mass due to aging and lower estrogen and testosterone.
- Genetic tendencies emerge after a lifetime of hormone fluctuations.
- Lifestyle changes that accompany midlife.
This increase in overall body fat leads to larger fat cells in the breasts as well as excess fat storage around the back, shoulders, and arms that make breast tissue seem fuller. Fat cells also produce some estrogen after menopause through the conversion of adrenal androgens, contributing to breast stimulation.
Abdominal Weight Gain
Weight gain specifically in the abdominal area alters hormonal dynamics to favor breast growth. Excess abdominal fat cells convert more adrenal androgens into estrogen through heightened aromatase enzyme activity. They also release cytokines and other immune factors that promote breast inflammation and fluid retention.
Insulin Resistance
Insulin resistance becomes more common as women age and gain weight, especially abdominal fat. Higher blood glucose and compensatory hyperinsulinemia promote growth of breast epithelial tissue. Insulin resistance is also associated with increased levels of prolactin and estradiol in menopausal women, both of which stimulate breast cell proliferation.
Inflammation
Insulin resistance and abdominal obesity are tied to whole-body inflammation, which can stimulate fluid retention in breast tissue. Inflammatory markers like interleukin-6 and C-reactive protein are often elevated in menopausal women with larger breast size.
Leptin Resistance
Leptin is a hormone produced by fat cells that helps regulate appetite and metabolism. In obesity, leptin resistance develops in which the brain no longer responds appropriately to leptin’s signals. Leptin also seems to play a role in mammary gland development. Leptin resistance in obesity allows leptin to overstimulate breast epithelial cell growth.
Medical Conditions
Some medical conditions that become more common at midlife and after menopause contribute to bigger breast size, primarily through promoting inflammation, fluid retention, and poor fat metabolism:
- Type 2 diabetes
- Hypertension
- Obstructive sleep apnea
- Metabolic syndrome
Chronic conditions like autoimmune disorders can also overstimulate breast inflammation and growth through effects on prolactin as well as direct action on breast epithelial cells.
Medications
Certain prescription medications that become more commonly used at midlife and beyond can instigate breast enlargement as a side effect. These include drugs for mental health, cardiovascular disease, diabetes, and osteoporosis.
Genetic Factors
Research shows that inheritable genetic variations make some women more prone to developing larger, denser breasts after menopause compared to others. Certain genotypes are associated with heightened sensitivity and responsiveness of breast tissue to estrogen and prolactin stimulation.
Breast Cancer Genes
Women with mutations in the BRCA1 and BRCA2 genes tied to higher breast cancer risk tend to develop more glandular breast tissue after menopause compared to noncarriers. This can translate to larger, lumpier breasts.
Receptor Genotypes
Specific polymorphisms in genes coding for estrogen receptor alpha, estrogen receptor beta, and the prolactin receptor are overrepresented in postmenopausal women with larger breasts.
Other Factors
A few other influences can come into play in determining changes in breast size and shape after menopause:
- Lack of regular exercise leads to fat gain and muscular atrophy.
- Poor posture and weak chest muscles allow breasts to sag more.
- Not having breastfed or having fewer children can limit premenopausal breast shrinkage.
- Smoking thin cigarettes enhances insulin resistance and breast inflammation.
No Post-Weaning Shrinkage
Breasts expand during pregnancy and remain enlarged during breastfeeding. After weaning, the breast lobules that produce milk usually shrink back down again. Women who haven’t gone through pregnancy and breastfeeding experience don’t get this deflating reprieve premenopause.
Never On Birth Control Pills
Since birth control pills contain estrogen and progesterone, they can inhibit the cyclic expansions of breast lobules through the menstrual cycle. Women who never took oral contraceptives may notice more breast enlargement perimenopause and postmenopause.
Conclusion
Multiple factors work together to promote breast enlargement during the menopause transition and postmenopause. Shifting hormone levels, especially lower progesterone and higher estradiol, alter breast cell composition to create larger, denser, more fluid-filled breast tissue. Weight gain, particularly increased abdominal fat, compounds these hormonal influences. Underlying genetic traits make some women more sensitive to these changes. Staying fit, managing weight, and seeking treatment for bothersome symptoms can help moderate undesirable breast enlargement after menopause.