How can I shrink the size of pituitary gland tumor (non cancerous)?

Depends on the type. Prolactinomas are common benign tumors of the pituitary and many respond to medications. Dopamine agonists such as bromocriptine, Cabergoline and pergolide will decrease the prolactin level and may, in some cases, shrink the tumor.
Depends in size. Most pituitary tumors are benign and less than a 1 CM (called micro adenomas). If that's the case, I typically leave it alone if shown to be not active hormonally. If active, I monitor size serially to make sure it's not enlarging. Of course you will need to discuss this with your doctor.

Related Questions

How serious is a small tumor on the pituitary gland? It is not cancerous. What are the chances of not being able to have kids?

Endocrine consults. It will depend on the cell type and hormone secretion and size and nature of the your doctor for treatment plan and follow ups.
Not high. Pituatury tumors are usually benign However they can create symptoms by either secreting hormones or by pressing on normal areas and causing hormone malfunction An endocrinologist can tell you what to do!
It depends. It is great that the small pituitary tumor is not cancerous. As long as it is not growing, observation may be an option. Due to the position of the pituitary, it cangrow and interfer with your vision. It can also disturb all of the hormones in your body since it secretes the regulatory hormones for your thyroid, adrenal glands, and ovaries. If these are disrupted, it will make it hard to conceive.
Iinfertility. All depends on the type of hormone they secrete. Prolactinomas (prolactin secreting adenomas) can reduce fertility until they are medically and/or surgically treated.
Complicated. Usually, these are simply followed with MRIs. Blood work should be obtained to see what type of tumor it is. Rarely does it interfere with having children.
How do you feel? This is a problem for fertility if, and only if, you are not having your normal cycles. With today's imaging, we're finding lots of these little things and many seem to do absolutely nothing.