Hormones are one possible cause of weight gain, but diagnosed hormone disorders are not the most common explanation. Weight is also affected by sleep, food intake, activity, age, medications and genetics.
Which Hormones and Conditions Can Cause Weight Gain?
The 5 main hormone-related causes or contributors are hypothyroidism, Cushing syndrome, polycystic ovary syndrome (PCOS), menopause-related changes and corticosteroid treatment.
| Cause or contributor | Weight-related clues | Other possible symptoms |
|---|---|---|
| Hypothyroidism | Slower energy use and weight gain | Fatigue, feeling cold, constipation, dry skin, hair changes and heavy or irregular periods |
| Cushing syndrome | Fat gain around the trunk and face | Thin arms and legs, easy bruising, muscle weakness, high blood pressure and purple stretch marks |
| PCOS | Weight gain may occur with insulin resistance | Irregular periods, acne, excess facial or body hair and scalp hair thinning |
| Menopause | More abdominal fat and a change in fat distribution | Hot flashes, night sweats, sleep problems and menstrual changes |
| Corticosteroid medicines | Weight gain and changes in fat distribution | Increased appetite, swelling, acne and other steroid-related effects |
Hypothyroidism
An underactive thyroid produces too little thyroid hormone. Thyroid hormones help regulate how the body uses energy, so hypothyroidism can contribute to weight gain.
Other symptoms can include fatigue, sensitivity to cold, constipation, dry skin, hair thinning and menstrual changes. These symptoms also occur with many other conditions, so fatigue and weight gain alone do not confirm a thyroid disorder.
Doctors usually start a thyroid evaluation with a thyroid-stimulating hormone (TSH) blood test. They may also measure free thyroxine, or free T4. Symptoms alone cannot diagnose hypothyroidism.
Cushing Syndrome and Cortisol
Cushing syndrome develops when the body is exposed to too much cortisol for a prolonged period. It can cause rapid or noticeable weight gain around the abdomen, upper body and face, while the arms and legs remain relatively thin.
Easy bruising, muscle weakness, high blood pressure, high blood sugar and wide purple stretch marks are other warning signs. Cushing syndrome is rare.
Everyday stress is not the same as Cushing syndrome. Stress can affect sleep, appetite and activity, but persistent cortisol excess requires medical evaluation. Doctors usually test for Cushing syndrome when the symptoms and medical history make it plausible. Initial tests can include late-night salivary cortisol, 24-hour urine cortisol or a dexamethasone suppression test.
PCOS, Insulin Resistance and Weight Gain
Polycystic ovary syndrome (PCOS) is a hormonal and metabolic condition associated with irregular ovulation, higher androgen levels and insulin resistance.
Weight gain can occur with PCOS, but a person with PCOS does not have to be overweight. Possible clues include irregular or absent periods, acne, excess facial or body hair, scalp hair thinning and darkened, thickened skin patches called acanthosis nigricans.
Doctors diagnose PCOS from the overall pattern of symptoms, medical history, examination and, when appropriate, blood tests or an ultrasound. A single "hormone imbalance" test does not diagnose PCOS.
Menopause and Estrogen Changes
During perimenopause and menopause, estrogen and progesterone levels decline. The body may use energy differently, and fat distribution may shift toward the waist. Sleep disruption can also make weight management more difficult.
Aging, muscle loss, changes in activity and other factors contribute as well. Menopause-related weight gain is not caused by hormones alone.
Menopausal hormone therapy is not a weight-loss treatment. It may improve symptoms such as night sweats and sleep disruption, which can indirectly help with weight control, but hormone therapy alone does not produce weight loss.
Medicines That Act Like Hormones
Long-term or high-dose corticosteroids, including prednisone, can cause weight gain and Cushing-like changes in body-fat distribution. Other medicines used to treat diabetes, depression, bipolar disorder and psychotic disorders can also promote weight gain.
Do not stop a prescribed medicine without speaking with the prescribing clinician.
How Can You Tell Whether Weight Gain May Be Hormonal?
Weight gain deserves a medical evaluation when it is unexplained, rapid or accompanied by symptoms such as:
- Persistent fatigue, feeling cold or constipation
- Irregular or absent periods
- New facial hair, severe acne or scalp hair loss
- Easy bruising, purple stretch marks or muscle weakness
- A rounder face or a new fat pad at the upper back
- Swelling in the legs, shortness of breath or sudden fluid-related weight gain
- Weight gain that began after starting a new medicine
A clinician will usually review your weight pattern, diet, sleep, medications, menstrual or reproductive history and other symptoms. Testing should match the suspected condition. Thyroid testing is commonly considered, while cortisol testing and reproductive hormone testing are usually guided by specific clinical signs rather than broad "hormone panels." If you take a hormone-related supplement such as DHEA, note the exact product and dose beforehand; for reference, this is how DHEA capsules sold online list their dose and ingredients.
The Bottom Line
The next step is a targeted medical evaluation, not an over-the-counter "hormone balance" supplement. If weight gain is sudden, persistent or accompanied by the symptoms above, speak with a primary care clinician or endocrinologist.