The Pituitary gland is a pea-sized gland that is situated just below the hypothalamus, which forms the top part of the brainstem and which then continues as the spinal cord.
If you imagine your head as a soccer ball, then the pituitary gland is situated right in the middle of it. The pituitary gland sits snugly in a bony pit called the sellar fossa.

When there is a sudden expansion of the pituitary gland, either from a tumour or bleeding, patients often complain of central deep-seated headaches that occur between their eyes and behind them.
However, most tumours that arise from the pituitary are slow growing, so that headaches are often not experienced.

The pituitary gland produces “master” hormones that stimulate other endocrine glands to develop and to produce hormones. So, if the pituitary gland is damaged, then other endocrine glands will not work properly.

The pituitary gland is made up of an anterior portion and a posterior portion, which produce hormones separately. The anterior pituitary hormones are gonadotrophins (luteinising hormone, and follicular stimulating hormone) which control the ovaries (oestrogen) and the testes (testosterone), growth hormone, adrenocorticotrophic hormone (ACTH), which controls adrenal hormone production, and thyroid stimulating hormone (TSH) which controls thyroid hormone production.