What Causes Gynaecomastia? Hormones, Drugs & Risks - Harley Street

Quick Summary

Gynaecomastia develops when there is a hormonal imbalance between testosterone and oestrogen, causing breast tissue to grow in men.
Common causes include puberty, ageing, certain medications, and some medical conditions.
It may need medical assessment and treatment if it affects your confidence and you notice some symptoms.

What is gynaecomastia?

Gynaecomastia is a common condition that causes enlarged breasts tissue in men. It is not just fat, but a glandular growth under the chest. Gynaecomastia is different from pseudogynaecomastia, which is the enlargement of the chest caused by excess body fat and not because of breast tissue growth. In true gynaecomastia, there is firm or rubber like tissue that grows behind the nipple.

Knowing the difference from these two is important because the treatment is not the same. Chest enlargement caused by excess fat may improve with weight loss, regular exercise, and lifestyle changes, while true gynaecomastia may need medical treatment or surgery if it does not go away on its own.

How common is gynaecomastia?

Gynaecomastia is a common condition that can happen in different stages of life.

Newborns: baby boys may develop temporary breast swelling because of hormones passed from their mother before birth. This disappears within a few weeks.
Puberty: Around 50% to 60% of teenage boys experience gynaecomastia because of hormonal fluctuation during puberty.
Older men: as men get older, testosterone levels naturally decrease. This change can make breast tissue more likely to develop.

The Hormonal Cause of Gynaecomastia

Hormonal imbalance is the root cause of all gynaecomastia cases. When oestrogen rises or testosterone falls, breast tissue can grow.

Testosterone deficiency

This means the body is producing less androgen than it should. This happen because of:

Ageing: testosterone levels naturally decline around 30 to 40 years old.
Hypogonadism: this is the condition where the testes do not produce enough level of testosterone
Chronic illness: conditions like kidney disease, liver disease, diabetes, or obesity can lower testosterone levels

When testosterone drops, the balance shifts towards oestrogen making breast tissue cells grow more easily.

Increased Oestrogen levels in men

Men need some oestrogen for bone health, brain function, and libido. But too much oestrogen can cause breast enlargement. There is one key process called aromatisation, where an aromatase (enzyme found mainly in fat tissue) converts testosterone into oestrogen. This can cause natural production of more oestrogen especially to men with higher body fat.

The liver function also contributes, if your liver is impaired due to disease, alcohol, or medications, oestrogen levels can increase.

Androgen receptor sensitivity

Gynaecomastia can also occur even if hormone levels in your blood tests look normal. This is because the body may not respond properly to testosterone. Testosterone works by attaching to special receptors in cells. If these receptors are less responsive because of genetics or cellular signalling issues, the body does not respond well to normal testosterone levels. The result will be similar to having low testosterone, and breast tissue will still grow. This is the reason why some men with normal hormone level tests still develop gynaecomastia.

Puberty Gynaecomastia

Why does it happen?

During puberty, hormone levels change quickly. In many boys, oestrogen spikes early and their testosterone rises more slowly. This temporary hormone imbalance can cause the breast tissue to enlarge.

Factors like weight gain, stress, or certain medications may make the condition more noticeable.

Does it go away on its own?

In most cases, yes. Puberty-related gynaecomastia is usually temporary and slowly disappears within 6 to 24 months as hormone levels become balanced.

But seek for a medical advice if:

It lasts more than 2 years
It is very large or painful
It is on one side only
There is nipple discharge

Persistent cases may need hormone tests, or sometimes surgery.

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What Medications Can Cause Gynaecomastia?

There are quite a few medications that cause gynaecomastia. These medicines can:

Block testosterone
Mimic oestrogen
Lower natural hormone production
Harm the liver so it cannot clear oestrogen

Common prescription drugs

Type of Drug	Examples	What It Does
Anti-androgens	Flutamide, Bicalutamide, Cypoterone	It directly blocks the testosterone
Prostate treatments	FInasteride, Leupromide	It lowers testosterone, raise oestrogen relative
Anabolic steroids	Misused testosterone or “boosters”	It suppress the natural production of testosterone
Antidepressants	SSRIs (e.g. Fluoxetine), some TCAs	It may increase prolactin, which can disrupt normal hormone balance in the body.
Heart medications	Spironolactone, Digoxin	It may block androgen (male hormones) or behave like oestrogen
Antifungals	Ketoconazone	It reduce testosterone production in the body
Opiates	Methadone, long-term opioids	It may lead to lower testosterone levels over time

If you are taking these medications, it is better to speak to your doctor. Do not stop taking these medicines without proper medical advice.

Over the counter and recreational substances

Alcohol: drinking too much alcohol can affect liver function, which may lead to lower testosterone levels, since the liver helps regulate hormones.
Cannabis: regular use has been linked to reduced testosterone levels.
Herbal products: some natural oils like tea tree oil and lavender oil may have oestrogen-like effects in the body.

How do these substances cause gynaecomastia?

There are three main ways that these causes breast enlargement:

Hormone suppression: less natural testosterone
Oestrogen-like effects: compounds that copies oestrogen
Liver interference: liver cannot properly break down oestrogen

Health Conditions That Can Lead to Gynaecomastia

Endocrine (hormone) disorder

Hypogonadism: testes do not produce enough levels of testosterone
Hyperthyroidism: overactive thyroid increases aromatase which can cause more oestrogen
High prolactin: lower testosterone

Liver and kidney disease

Liver disease (cirrhosis, hepatitis, alcohol damage): oestrogen is not cleared well
Kidney disease: it can affect hormone balance and lower testosterone

Tumours (rare)

Some tumours produce hormones that shift the balance:

Testicular tumours
Adrenal tumours
Pituitary tumours

These are uncommon, but they must be checked if gynaecomastia:

Suddenly appears
Is one-sided
Comes with weight loss, fatigue, or other weird symptoms

Lifestyle Factors That Play a Role

Obesity

Obesity is a big factor. Fat tissue contains aromatase, which turns testosterone into oestrogen.

Also with obesity, it is harder to see if the chest is bigger because of:

Fat only (pseudogynaecomastia)
Gland tissue (true gynaecomastia)

A clinical exam or ultrasound can tell the difference.

Ageing

As men get older:

Testosterone level drops
Body fat increases
Liver function may slow

Because of this, many men over 50 develop mild gynaecomastia naturally.

When Should You Be Concerned?

Most cases of gynaecomastia are harmless. But you should see a doctor if you notice any of the following:

The chest swelling is growing quickly over a few weeks or months.
There is pain, discomfort, or tenderness in the chest area.
Only one side of the chest is enlarging.
There is nipple discharge, especially if it is bloody.
Swelling that does not improve after puberty.

What do your doctor may do

To find the cause, your doctor may recommend:

Blood tests to check hormones like testosterone, oestrogen, LB, FSH, prolactin, and thyroid hormones.
Imaging tests like ultrasound or mammogram to look at breast tissue and rule our serious conditions like tumours.
Review of medications to see if any drug or supplements you are taking could be contributing.

These tests help your doctor identify the cause and recommend the right treatment.

Treatment Options

Treatment depends on your age, the cause, and how long you have had it.

Option	When It Is Used	What It Involves	Key Points
Wait and see	Pubertal gynaecomastia Early and mild cases	No treatment initially Regular check-ups	Most pubertal cases go away in 1 to 2 years
Medicines	Confirmed hormonal imbalance Early stage of gynaecomastia	Testosterone replacement if deficient Oestrogen blockers in some cases	Long standing gland tissue becomes firm and rarely shrinks much with medicines alone
Surgery	Persistent gynaecomastia Painful cases Affects confidence or daily life	Liposuction Gland excision	Effective for long-term solution Done under general anaesthesia Permanent results once gland is removed

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The Bottom Line

The main cause of gynaecomastia is hormonal imbalance, too much oestrogen compared to testosterone.
Key triggers are: puberty, ageing, medications, obesity and some health conditions.
Androgen receptor sensitivity can cause it even when hormone levels tests look normal.
Most cases are benign, but persistent, sudden and painful gynaecomastia needs a medical check.
Treatment can vary depending on your situation.