Hello
Thanks for the query.
This a problem whereby hyperpigmentation is caused by insulin resistance,which has occurred due to PCOS. This hyperpigmentation is characterized by large areas of the skin developing a darker color but with no specific boundary to separate the area from the ‘normal’ skin. This type of hyperpigmentation is typically found within body folds, under the armpits and in the groin area.
 
There are several ways to get rid of hyperpigmentation, including natural remedies and medicated creams. There’s also the option to remove the marks with laser treatment.
Hyper pigmentation creams have hydroxyquinine in them and for that you have to consult a dermatologist for the prescription
 Home Remedies for hyper pigmentation...
Milk & Honey Face Pack – Mix together 1 tsp. of milk powder, 1 tsp. of lemon juice, 1 tsp. of honey and 1 tsp. of almond oil. Apply the pack to your face or body in the same way as you would apply a moisturizer – rub it in and then leave it on for at least 20 minutes. Once it’s settled into the skin, wash it off, and then moisturize your skin. Use this pack at least three times a week for up to a month to notice a difference. 

Oatmeal and Tomato Juice Scrub –  Mix together equal parts oatmeal, curds, and tomato juice until they form a paste that will stick to your skin without falling off. Rub the paste into your skin and leave it for ten minutes, then rinse it off with warm water. 

You must consult a endocrinologist and a dermatologist so that your problem of hyperinsulinemia and hyper pigmentation are taken care of simultaneously.

Normally following methods are used to tackle insulin resistance.
1...reduction of weight
2...doing good amount of regular exercises daily.
3... Taking METFORMIN 500 mg twice a day for at least 6 to 9 months.

I hope to have answered your query however you may revert to me for any further query.
Best of luck
Thanks

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