Many individuals with obesity who experience darkening of the skin on their neck often attribute it to poor hygiene, sweat accumulation, or skin darkening. However, according to Dr. Le Thanh Huyen, Department of General Internal Medicine at Tam Anh General Hospital, Hanoi, this could be an early sign of a metabolic disorder related to insulin resistance, leading to acanthosis nigricans. Here are some of the causes.

Insulin resistance: When the body doesn't respond well to insulin, the pancreas produces excess amounts of this hormone, stimulating excessive skin cell growth. This leads to skin thickening and increased pigmentation. It's also an early warning sign of prediabetes or type 2 diabetes.

Rapid weight gain: Sudden or excessive weight gain in a short period disrupts the body's endocrine and metabolic systems, promoting the symptoms of acanthosis nigricans. Dr. Huyen explains that rapid weight gain is often accompanied by visceral fat accumulation and hormonal imbalances—factors linked to acanthosis nigricans. Obesity accelerates the aging process, weakening the natural barrier against UV rays. This reduced sun protection makes the skin more susceptible to uneven melanin production, leading to dark, thickened patches.

Dr. Huyen consults with a patient. Illustrative photo: *Tam Anh General Hospital*

Inflammation: A weakened immune system in obese individuals creates opportunities for bacteria and fungi to cause inflammation. Prolonged skin inflammation not only damages the skin structure but also creates a favorable environment for acanthosis nigricans to develop.

Certain medications: Some medications like corticosteroids, growth hormones, and contraceptives containing estrogen or androgen can affect hormones and increase the risk of insulin resistance. Prolonged or improper use of these medications can accelerate the spread of acanthosis nigricans. Dr. Huyen advises obese individuals to be cautious and use medication only as prescribed to avoid complications.

Chronic diseases: Polycystic ovary syndrome (PCOS), hypothyroidism, and fatty liver disease are often accompanied by endocrine and metabolic disorders, increasing the risk of skin pigmentation disorders. Treating the underlying condition can significantly reduce skin problems for many patients. Screening and treating chronic diseases contributes to managing acanthosis nigricans symptoms.

Minh Anh