What causes hyperplasia of a gland?

Which gland: Different glands have different stimuli to which they respond. Breast responds to sex hormones, adrenal responds to ACTH, some glands enlarge, though not strictly hyper-plastic due to inflammation, e.g. salivary glands. You may view this site: https://medlineplus.gov/ency/article/003441.htm For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex.