The Hypothyroidism
What is the thyroid gland?
The thyroid gland is an endocrine gland that
secretes its hormones directly into the blood, it looks like a butterfly in
shape and it is formed of three lobes right lobe, left lobe, and pyramidal lobe
connected by an isthmus.
It sits opposite C5 to T1 on front of the neck
and it synthesizes and secretes three hormones into the blood, that's hormones
are:
1.
Thyroxine [T4].
2.
Triiodothyronine [T3].
3.
Calcitonin.
Thyroxine [T4] represents more than 89% of the
output of the thyroid gland but Triiodothyronine [T3] is the most powerful and
active hormone from Thyroxine [T4] and calcitonin.
What is the function of the thyroid gland?
Most of the Thyroxine [T4] hormone converted
to Triiodothyronine [T3] which has biological action and also some of Thyroxine
[T4] converted to reverse Triiodothyronine [rT3] which has not biological
action.
Thyroid hormones have 2 types of actions:
1.
On the whole body.
2.
Inter-cellular action.
There are many functions of Thyroid hormones, but I will mention some of them briefly:
- The most important function of
the thyroid hormones is the stimulation of development, growth, and
function of the central nervous system which leads to normal mental growth.
- They are important to stimulate
the secretion of milk during lactation.
- They are essential for
fertility and the normal menstrual cycle.
- Thyroid hormones are important
for teeth eruption and development.
- Also thyroid hormone control
body metabolism and energy production through stimulating uptake glucose
by cells, oxygen consumption, basal metabolism, and heat production.
- They increase systolic blood
pressure.
- Thyroid hormones increase heart
rate and stroke volume.
- They increase the depth and
rate of breath.
- They increase glucose
absorption from digested food by the intestine and increase appetite.
- Thyroid hormones stimulate with
carotenes to synthesis vitamin A.
- Thyroid hormones stimulate the utilization of all vitamins.
What are the factors control the functions of the thyroid gland?
There are many mechanisms and factors affect
and control the function of the thyroid gland I will mention some of them
generally:
First, the thyroid-stimulating hormone [TSH]
is most important to control the size of the Thyroid gland and amount of
Thyroxine [T4] and Triiodothyronine [T3] secreted from the thyroid gland.
Second, exclusively in females during
pregnancy, the placenta secretes a hormone similar to the thyroid-stimulating
hormone [TSH] which is called human chorionic gonadotropin [chg.] which leads
to increase thyroid gland activity and therefore the number of thyroid hormones
secreted from the thyroid gland will increase during pregnancy.
Third, people which live in a cold environment
the number of Thyroid hormones increase because the thyroid gland is stimulated
by the cold environment to heat production to counteract the effects of low
temperature.
And other factors like age, race, a diet low in iodine, antithyroid agents [Goitrogens], and exposure to stress.
What is Hypothyroidism?
We can describe hypothyroidism as follow it is
the inability of the thyroid gland to secrete a sufficient number of Thyroid
hormones due to many causes. It is also called underactive thyroid.
Hypothyroidism commonly affects females than males and also it affects people over 6o years old more than people under 60 years old.
What are the causes of Hypothyroidism?
The first common cause of hypothyroidism is
inflammation of the thyroid gland due to the immune system attack the thyroid
gland through immune cells, it is called Hashimoto`s thyroiditis [also called
autoimmune thyroiditis]
10:1 it is the ratio from Female to Male which
get hypothyroidism.
1.
The thyroid gland becomes larger than the normal size of the
thyroid gland but in the late, the thyroid gland becomes smaller than the
normal size of the thyroid gland which causes hypothyroidism.
1.
Surgical removal of a part of the thyroid gland and survive
small part of the thyroid gland not enough to meet the needs of the body from
Thyroid hormones, that's maybe happened in a thyroid cancer patient.
1.
Some conditions like goiter treated by radioactive iodine
therapy which also kills many cells of the thyroid gland and left a small part
of the thyroid gland and therefore the thyroid gland can not produce enough
amount of thyroid hormones which lead to cause hypothyroidism but it is
temporarily for one or two years then the thyroid gland recover the lost cells
and becomes normal again.
1.
In some cases of hypothyroidism, the thyroid gland was normal
and was not has any problem but not produce enough amount of thyroid hormones,
here the problem in the pituitary gland not in the thyroid gland, the pituitary
gland does not produce enough amount of the thyroid-stimulating hormone [TSH]
which stimulate the thyroid gland to produce enough amount of the thyroid
hormones which meet the needs of the body.
1.
The cause may be congenital which called congenital
hypothyroidism [CHT], it is due to absent or abnormal development of the
thyroid gland or the thyroid gland is normal but there is a problem in their
function can not make thyroid hormones.
The development of the thyroid gland starts
very early in pregnancy, in the normal condition the thyroid gland forms at the
back of the tongue then moves to its normal site on the front of the neck on 8
weeks but in abnormal conditions, the gland does not move to the normal site on
the front of the neck, this condition called Dysgenesis.
In other conditions, the thyroid gland develops and moves to its normal site but there is a problem in makes of thyroid hormones, this condition called Dyshormonogenesis.
And other causes like take certain medications e.g.: amiodarone or lithium
What are the symptoms of hypothyroidism?
There are general symptoms of hypothyroidism
it is:
- Constipation.
- Slowing mind.
- Slow pulse.
- Dry, pale, and cool skin
- Delayed reflex.
- Cold intolerance.
In some details:
The hypothyroidism in human infants due to congenital hypothyroidism [CHT] or deficiency of iodine in the diet of the mother during pregnancy is called cretinism.
Clinical features of cretinism:
- Retardation of mental,
physical, and sexual growth.
- Yellowish skin due to
carotenaemia due to defect in the synthesis of vitamin A which also causes
thick and scaly skin with scanty coarse hair.
- Low basal metabolic rate [BMR].
- Low oxygen consumption.
- Thick lips and puffy eyelids.
- Swollen tongue.
- Umbilical hernia and abdomen protuberant.
In cases of adult humans of hypothyroidism for a long time without treated is called myxedema, which characterized by:
- Defect in mental processes as
lack of concentration, long reflex time, and sleepiness.
- Also, a low basal metabolic
rate [BMR] and oxygen consumption.
- Skin becomes thick due to the
deposition of a protein substance called myxedematous tissue.
- The skin becomes yellowish.
- Increase sensitivity to cold.
- Failure of sexual function.
- Increase the blood level of cholesterol and triglyceride.
What are the diagnostic methods of hypothyroidism?
The doctor diagnosed hypothyroidism based on a combination of symptoms, thyroid blood tests, and other many factors.
Thyroid blood tests as:
- Thyroxine [T4] test.
- Triiodothyronine [T3] test.
- Thyroid-stimulating hormone [TSH] test.
How to treat the hypothyroidism?
Treatment of hypothyroidism differs from patient to other patients according to the cause of disease.
I will mention some of the methods of
treatment of hypothyroidism:
- Take the synthetic form of
thyroxine [T4] as levothyroxine.
- Increase the amount of iodine
intake in the food.
- Take the synthetic form of
Triiodothyronine [T3] as liothyronine but it has more side effects than
levothyroxine especially in a cardiac patient.
Finally, we must be careful about our health
to continue in healthily building our community and I wish you health and
wellness.
Written by:Mohammed
AbdElaziz
Edited by: Alaa Mahmoud
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