Page 55 - 86 human physiology part-2

Chapter 14

sexual immaturity. Sometimes the thyroid gland produces too much thyroxine, a condition known as
hyperthyroidism. This condition produces symptoms such as an abnormally high body temperature,
profuse sweating, high blood pressure, loss of weight, irritability, and muscular pain and weakness. It
also causes the characteristic symptom of the eyeballs protruding from the skull called exopthalmia.
This is surprising because it is not a symptom usually related to a fast metabolism. Hyperthyroidism
has been treated by partial removal or by partial radiation destruction of the gland. More recently,
several drugs that inhibit thyroid activity have been discovered, and their use is replacing the former
surgical procedures. Unfortunately thyroid conditions require lifetime treatment and because of the
body's need for a sensitive balance of thyroid hormone both supplementing and suppressing thyroid
function can take months or even years to regulate.

T3 and T4 Function within the body

The Production of T3 and T4 are regulated by thyroid stimulating hormone (TSH), released by the
pituitary gland. TSH Production is increased when T3 and T4 levels are too low. The thyroid hormones
are released throughout the body to direct the bodies metabolism. They stimulate all cells within the
body to work at a better metabolic rate. Without these hormones the bodies cells would not be able to
regulate the speed at which they performed chemical actions. Their release will be increased under
certain situations such as cold temperatures when a higher metabolism is needed to generate heat.
When children are born with thyroid hormone deficiency they have problems with physical growth and
developmental problems. Brain development can also be severely impaired

The significance of iodine

Thyroid hormone cannot be produced without an abundant source of iodine. The iodine
concentration within the body, although significant, can be as little as 1/25th the concentration within
the thyroid itself. When the thyroid is low on iodine the body will try harder to produce T3 and T4
which will often result in a swelling of the thyroid gland, resulting in a goiter.

Calcitonin

Calcitonin is a 32 amino acid polypeptide hormone. It is an additional hormone produced by the
thyroid, and contributes to the regulation of blood calcium levels. Thyroid cells produce calcitonin in
response to high calcium levels in the blood. This hormone will stimulate movement of calcium into
the bone structure. It can also be used therapeutically for the treatment of hypercalcemia or
osteoporosis. Without this hormone calcium will stay within the blood instead of moving into bones to
keep them strong and growing. Its importance in humans has not been as well established as its
importance in other animals.

Parathyroid gland

There are four parathyroid glands. They are small, light-colored lumps that stick out from from
the surface of the thyroid gland. All four glands are located on the thyroid gland. They are butterfly-
shaped and located inside the neck, more specifically on both sides of the windpipe. One of the
parathyroid glands most important functions is to regulate the bodies calcium and phosphorus levels.
Another function of the parathyroid glands is to secrete parathyroid hormone, which causes the release

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