Overview
Many boys with Klinefelter aren't diagnosed until puberty or when trying to have children.
Testosterone helps with energy, muscle, and bone health.
Symptoms
Common signs:
- Small testicles
Less common
- Tall height
- Learning delays
- Breast growth
Look up a symptom: Low sex drive · Swollen breast tissue in a male · Trying to get pregnant without success
When to get medical care
Call 911This isn't an emergency by itself. Call 911 for trouble breathing, chest pain, or fainting.
Get care todayNew or worse symptoms, or symptoms with fever.
See a doctor soonPuberty concerns.
Causes
Extra X.
Does it spread or run in families?
- It isn't contagious. You can't catch it from someone else.
Diagnosis
A clinician asks about your symptoms and may order tests.
The exam
A physical exam.
Tests
Tests, if needed:
- Chromosome test:
Treatment
Treatment depends on the cause and how severe it is.
Self-care
- Ask about testosterone therapy
- Do physical activity
Which doctor treats this
- Start with your primary care provider (family doctor or internist).
- They may send you to an endocrinologist (hormone doctor).
Children, pregnancy, and older adults
- Teens: Starting testosterone at puberty helps.
- Boys: Often found at puberty.
Outlook
Most live healthy lives.
Most live full lives.
Getting ready for your visit
Bring a list of your symptoms and medicines.
What to bring
- A list of your medicines and supplements
- Notes on when symptoms started and what makes them better or worse
Questions to ask
- What's causing this?
- What treatment do you recommend?
- What are my fertility options?
Research studies
Research studies test new ways to find and treat health problems. Some are looking for volunteers. Talk with your doctor before joining one.
Search ClinicalTrials.gov for studies on Klinefelter syndrome
Sources
Last updated 2026-11-12.