It is important to understand the principle of negative feedback to be able to understand the regulatory function of this gland . The thermostat controlling the geaser that supply hot water to our homes works on this principle.(negative feedback). Imagine that the thermostat is set to 60 degrees Celcius. If the tmeperature of the water rises above 60 degrees the power supply is cut but if the temperature goes below 60 degrees the thermostat reconnects the power.

The pituitary works on the same principle. It produces two hormones that stimulate the ovaries to produce oestrogen. The two hormones are known as FSH (Folicle Stimulating Hormone) and LH ( Luteinising Hormone). If the oestrogen levels are low the pituitary gland produces more FSH and LH . The FSH and LH stimulate the ovary and it producesmore oestrogen. If the oestrogen levels are high the pituitary gland produces less FSH and LH and hence the ovary produces less oestrogen. In a normal healthy female the oestrogen , FSH and LH levels are regulated within narrow margins.

The next diagram illustrates the relationship between the ovaries and pitiutary.

Following ovulation , the corpus luteum appears . It has a limited live span and LH plays a posible role in its function. Normal LH levels levels won't be able to expand this live span beyond ten days.

In the condition known as polycystic ovarian syndrome (PCO) the LH levels are usually increased.

After the menopause the ovaries ceased to produce oestrogen and the FSH and LH levels become very high in an effort to stimulate the non responding ovaries (see MENOPAUSE).

The pituitary also produces another important hormone called PROLACTIN. One of prolactin's most important functions is stimulating the breasts to produce milk. Excessive prolactin production in non lactating women causes ovarian dysfunction with anovulation ( the ovary stops producing egg cells).