Causes of Dark circles can be hereditary, lack of sleep, lack of nutrition, allergies, frequent rubbing of eyes, smoking, UV radiation, hemoglobinopathies etc. The treatment comprises of few instructions given below along with certain Multivitamins -Antioxidants supplements, under eye creams, chemical peels, lasers and fillers. You can consult any Dermatologist for the same. Few instructions: (1) Cold compress to the eyes 3 times a day (Can dip clean cotton in refrigerator cold water and keep over closed eyes for 30 seconds) (2) Healthy nutritious diet (3) Adequate sleep for at least 7-8 hours (4) Adequate water intake at least 3-4 litres / day (5)Do not rub the eye

Dark circles can be due to general health issues / normal body type etc... You can improve general health by managing lifestyle Good eating/ sleeping habits Less screen time Vitamin supplements Managing co morbid condition..like thyroid in your case Home remedies ..also under eye creams too for decreasing pigmentation  If all this dont help...you hv the option for fillers etc..any occuloplatic surgeon / plastic surgeon/ cosmetologist can help.