Addison's disease and other sources of adrenal insufficiency , in which hormones that stimulate melanin synthesis (e.g. MSH ) are frequently elevated.
Cushing's disease , excessive ACTH production; Melanocyte-Stimulating Hormone ( MSH ) production is a byproduct of ACTH synthesis from Pro-opiomelanocortin ( POMC ).
Melasma ( chloasma ), or patchy hyperpigmentation often found in pregnant women, women taking oral contraceptives, 10% of nonpregnant women and dark skinned men. It is usually found on the forehead, temples and cheeks. It usually fades slowly and completely after childbirth or cessation of hormone use. However in men, melasma slowly fades and incompletely after childbirth. In men, melasma rarely fades.
linea nigra , a hyperpigmented line found on the abdomen during pregnancy
Certain chemicals such as salicylic acid , bleomycin , and cisplatin
Another form of hyperpigmentation called post-inflammatory skin darkening is a common occurrence after irritation or injury to the skin, such as the after effects of waxing or hair removal or any kind of puncture to the skin. This type of hyperpigmentation is more prominent in dark skin, however it can also be seen in individuals with lighter skin. After irritation or injury to the skin, the pigment cells (melanocytes) deposit pigment in both upper and lower layers of the skin. However these dark patches clear with time although they can last for months to years. If treatment is started immediately, this would help determine the outcome and ultimate appearance of the area.
Avoiding the sun keeps the condition from worsening and treatment depends on whether the pigmentation is epidermal or dermal. Therefore you will have to firstly identify the areas involved. If you can identify a source, such as over exposure to the sun or ingestion of a medication you should do your best to decrease or eliminate that source. This is because once the skin is sensitized, the melanocytes become hypersensitive and will repigment readily, if restimulated.It is therefore essential to protect screen yourself from over exposure to the sun as it may aggravate all of the above conditions.
Hyperpigmentation can be treated by using skin whitening products such as bleaching creams which contain hydroquinones and mild acids such as glycolic, kojic and retinoic acid. Hydroxy acid peels can also be used as they exfoliate and help lighten the skin. These peels can be used at home once or twice a week. A number of effective laser treatments are also available on the market to help remove pigments without scarring.