Some information about the hypothalamus and pituitary gland

The hypothalamus and pituitary gland are essential for normal sexual development. These tiny glands are located at the base of your brain, as shown in Figure 3. Your hypothalamus (item 1) is an important endocrine gland only about the size of a thumbnail. It is your malfunctioning hypothalamus which is the principal reason for you having Kallmann's syndrome (see answer to Question 7).

Your pea-sized pituitary gland (item 3) is connected to your hypothalamus by a tiny structure called the pituitary stalk (item 2) containing a rich network of tiny blood vessels or capillaries. Although they are not actually endocrine glands themselves, the two olfactory bulbs (item 4) are normally connected to the brain. These are essentially "relay" stations that receive nerve impulses from your nose (in response to a smell stimulus) and transmit it to that area of your brain where you experience the sense of smell. As a person with Kallmann's syndrome, you were born with only very basic or completely absent olfactory bulbs. Since the olfactory bulbs are necessary for a normal sense of smell, you are therefore anosmic.

As you already know, your endocrine glands often work together in teams. Once your hypothalamus secretes one of its many different hormones, it is delivered to your pituitary gland via the pituitary stalk. Your pituitary gland is then encouraged to secrete hormones of its own which then circulate in the blood until their respective targets have been "hit". This teamwork is essential for a number of physical and biological processes to be carried out in your body. One of these processes is the regulation of sexual development by the hypothalamus, pituitary gland and the gonads (testes in men, ovaries in women) as members of an endocrine team known collectively as the hypothalamic-pituitary-gonadal axis.

As you can see from Figure 4, hypothalamic hormones target the pituitary gland and normally, pituitary hormones are released in response which then target the gonads. These pituitary hormones have two main functions: to encourage and maintain the body's secondary sexual characteristics as well as to promote fertility. The feedback mechanisms linking the gonads to the hypothalamus and pituitary gland normally ensure that these hormones are always available in the correct amounts.