Endocrinology is the study of the body’s hormones. Hormones can be likened to chemical
letters that circulate around the body in the bloodstream and letters come from a post
office and that post office is in deep in the middle of the brain. If you can see, this
tiny little gland here right in the middle of the brain is called the pituitary gland.
It receives messages from above in the hypothalamus. This is a larger diagram. The pituitary itself
is split into two halves—the front part and a back part. From the back part of the gland,
you’ll see that there are messages that control our water balance and our thirst. That's a very vital
function and the amount we drink. The front of the gland are messages that control our
growth, that tell us when to go into puberty, functions that we take for granted, our fertility
are very important messages for stress itself the cortisol function, which is our fight-flight
response and is the reason why we get jet lagged. Of course also the thyroid gland which
is important for metabolism. The pituitary gland is responsible for controlling
vital functions that we take for granted. Together with the hypothalamus, it constitutes
the most important endocrine organ and is the master gland. It’s responsible for
many conditions that we take for granted listed on this responsible for many, many conditions
that we take for granted and in controlling a loss of the functions of the target glands in the body.
The pituitary gland may be malformed from
birth. Embryologically, it develops as an out pouch from the mouth and grows upwards.
It’s actually sit outside the brain and you can reach it through the nose surgically.
It is connected up to the brain through the pituitary stalk. Sometimes, if the brain area doesn't
develop properly, you can see from where it is positioned in the brain that it may be
very close to the optic pathways in the hypothalamus. If the babies are born without development
in this area, it may include blindness as well as hormone deficiencies and a hypothalamic
disorder, which may include weight loss or weight gain and early and dysfunctional puberty.
The other reason why the pituitary may be malfunctioning is because of pituitary tumors that either
grow in pituitary itself such as a pituitary adenoma which may be non-functioning or can sometimes
also produce hormones of its own. There maybe other non-functioning adenomas or craniopharyngiomas
that arise in the pituitary and more malignant tumors that occur in the pituitary stalk.
Also tumors of the optic pathway can grow down and compress the pituitary.
Any tumour, or indeed the treatment for that tumor in that area can cause the pituitary to malfunction. It’s
important to have just the right amount of a hormone. Not too much and not too little.
As I said, there are tumors like pituitary tumors that can make too much of one particular
hormone squashing out the others. But there are also other tumors that grow down into
the pituitary.
The symptoms of a malfunctioning pituitary
depend on the cause. For example, if you have a tumor that's making too much hormone, you
will get symptoms of that. You might grow too fast if you have too much growth hormone
or you might get very heavy if you have too much cortisol. If at the same time that expansion
of the tumor or the malfunction of the pituitary includes deficiency, then you will grow less
well, you may not develop in puberty and you may not develop fertility in the future. If
you are an older child, your physical development may begin and then arrest, you may need help
to complete it. If you have malfunction of the back of the
pituitary gland you may get very, very thirsty and drink lots and lots of water and pass
lots of urine. Something that's reminiscent of sugar diabetes and that's why it’s called
diabetes but it’s diabetes insipidus because the urine is very clear and dilute because
what you are lacking is the hormone that allows you to concentrate water and retain water
and that is also potentially life-threatening situation and may herald some disorders of
the pituitary gland or some particular tumors affecting that area and is an important condition
but is not always well recognised and one that's not important not to miss.
Obviously, if you erode a lot of the hormones in the pituitary and are deficient of all
of the hormones, something that we call panhypopituitarism.That can creep up on you but you are at a
potential life-threatening risk when there is an intercurrent illness or crisis or if
you're knocked down by a bus. These are potentially life-threatening deficiencies.
If we go back to the post office idea, you can see that the pituitary gland produces
a number of different messages for each hormone, sorry, for each target gland and then in response, the target
gland has to produce a response. If we take a common problem like thyroid dysfunction,
here is the thyroid stimulating or TSH message to the thyroid gland. If the thyroid gland
is not working, you won’t produce thyroid hormone or thyroxine.
If the pituitary isn't working, you won’t produce thyroxine either, but you can differentiate
between the two because in this case, if the pituitary is working and the thyroid gland
is not working, pituitary will push more and more TSH, thyroid stimulating hormone, and that is high. It’s a bit like
trying to push on a blocked sink. You will put lots more water in to try and make the
thyroid gland respond. That’s the most common form of underactive thyroid hypothyroidism.
However, if the pituitary isn’t working, the TSH will be low and so will the thyroxine.
Then you can differentiate whether the problem is here or the problem is in the pituitary.
The same is true with fertility. If the problem is in the ovary or the testes, you will get
very high messages of LH and FSH with the pituitary trying to drive the organs to produce
their relative hormone responses. If the pituitary isn't working, these messages as well as the
oestrogen and testosterone, female and male hormones, respectively, will be low.
The treatment of a deficiency is replacement therapy. We have all the hormones, we can
replace them. Most of them by tablets, but some require injections, for example growth
hormone. Actually, replacement therapy for an endocrinologist is very rewarding because
we’re replacing normality. There should be absolutely no side effects of our treatment.
We should aim to give the right amount in the most natural form. For example, female
hormone replacement therapy can be given in a gradually increasing dose to induce puberty
in a girl and can give it in very natural ways with natural hormones and even through
transdermal preparations. We have very physiological ways of replacing
that do not cause any side effects for all these hormones including growth hormone, female
hormone, male hormone, replacing anti-diuretic hormone. It’s a very rewarding treatment
that we can give.