Acanthosis Nigricans

Acanthosis nigricans is caused by various conditions that lead to the activation of growth factor receptors which stimulate the proliferation of skin cells, such as keratinocytes and fibroblasts, ultimately leading to darker skin. These conditions can be either benign or malignant.

Causes of benign acanthosis nigricans include insulin resistance when the cells in the liver, adipose tissue, and muscles become insensitive to insulin and its effects. Therefore, these cells become less capable of glucose intake from the bloodstream. Insulin resistance can ultimately develop into type II diabetes mellitus, another cause of acanthosis nigricans. Moreover, acanthosis nigricans can also occur in individuals with polycystic ovarian disease, a syndrome typically in those assigned to females at birth, characterized by symptoms related to excess androgen production (e.g., hirsutism, acne, insulin resistance, and irregular or absent menstrual cycles). Other benign causes include hypothyroidism, which occurs when there is a lack of thyroid hormones; and Cushing syndrome, which is a set of symptoms resulting from exposure to elevated levels of the stress hormone cortisol due to exogenous glucocorticoid medication use, a tumor of the adrenals or a tumor of the pituitary gland. Additionally, acanthosis nigricans has been associated with administering certain medications, such as oral contraceptives, corticosteroids, and vitamin supplements, like niacin. 

On the other hand, malignant acanthosis nigricans can be caused by various malignant tumors, such as stomach, colon, and liver cancer, as well as lymphoma. 

Finally, various factors can increase the risk of acanthosis nigricans, including positive family history and a personal history of obesity. 

Treatment of acanthosis nigricans primarily involves identifying and treating the underlying medical condition. Weight loss and antidiabetic medications (e.g., metformin) can help manage insulin resistance and diabetes mellitus. For polycystic ovarian syndrome, treatment may include oral contraceptives and metformin, a diabetic medication, to regulate the menstrual cycle; weight loss and antidiabetic medications, such as metformin, to improve insulin resistance; spironolactone to treat hirsutism, as well as clomiphene citrate to help induce ovulation if fertility is desired. Hypothyroidism can be managed with thyroid hormone supplementation, while treatment of Cushing syndrome may include either decreasing or discontinuing glucocorticoid medications or removing the tumor surgically or radioactively. Discontinuation of medications that are related to the condition may also be considered. In cases of cancer, surgery, chemotherapy, or radiotherapy may be necessary.