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Cretinsm
1.
2. THYROID GLAND
It is endocrine gland
which drain
secretion into blood
stream directly.
It locates in the
neck
Consists of two
lobes connected by
isthmus
Secret t3 and t4
hormones
3. Thyroid
Gland
stroma
C.T capsule Trabeculae Reticular C.t
parenchyma
Thyroid
Follicles
Principle
follicular
cells
Para
follicular C
cells
Inter
follicular
cells
HISTOLOGY OF THYROID GLAND
4. THYROID FOLLICLE
Spherical in shape.
Lined by two types of cells:
1- principle follicular cells .
secret T3 and T4 hormones.
2- Para follicular C cells.
secret calcitonin.
Contain acidophilic colloid in the center
which contain stored hormones.
17. FUNCTIONS OF THYROID HORMONES
Metabolic effect: (generally increase BMR.)
on CHO metabolism:
- increase absorption of CHO from GIT .
- enhance gluconeogenesis and glycolysis .
on protein synthesis
small dose of thyroid hormone increase rate of
formation of proteins
Large dose of thyroid hormone lead to catabolism
of muscle protein
On fat metabolism
Accelerate lipolysis
Lower the level of cholesterol , phospholipids and
TAG
18. Thyroid hormone is necessary for hepatic
conversion of carotene to vitamin A
Effect on skeletal growth and development
required for production and action of growth
hormone and insulin like growth factor
On nervous system
Promotes growth and development of the brain
during the fetal life for the first few years
Essential for normal myelination of nervous system
in infant
On sexual functions
Essential for normal menstrual cycles and fertility
They increase milk secretion in lactating women
19. ON NERVOUS SYSTEM
Thyroid hormone promoted growth and
development of the brain during fetal life & for the
first few years of life.
The thyroid hormone are essential for normal
myelination & development of the nervous system.
In infant. If there is a deficiency in thyroid hormone
growth & maturation of the brain is retarded,
myelination is defective, the reflex time is
prolonged.
In adult, thyroid hormone causes an increased
response of the brain to catecholamine & increase
activation of reticular activating system.
An excess of thyroid hormone leads to restlessness
20. ON SEXUAL FUNCTIONS
For normal sexual function to act thyroid hormone
secretion needs to be approximately normal.
Thyroid Hs. Are essential for normal menstrual cycles
and fertility.
They increase milk secretion in lactating women.
ON GASTRO INTESTINAL TRACT
They increase the rate of secretion of the digestive juice
and motility.This leads to increase appetite and food
intake.
On respiration
Thyroid hormone increase respiration due to increase
rate of metabolism which increase the utilization of
oxygen & the formation of carbon dioxide.
21. THE CARDIOVASCULAR SYSTEM
thyroid hormone increase the number & affinity of
beta-1, adrenergic receptors in the heart, also it
increase its sensitivity catecholamine (catecholamine
increases all properties of the heart).
Increased metabolism in the tissues causes more rapid
utilization of oxygen & greater metabolic end products
to be released from the tissues.These effects cause
vasodilatation, thus increasing the rate of blood flow in
the skin for heat elimination.
Increase blood flow leads to increase venous return
leading to increase in cardiac output so the systolic
blood pressure thus, pulse pressure is increased.
The hormone slightly increase the blood volume, partly
from vasodilatation and partly secondary to its
22. CONGENITAL HYPOTHYROIDISM
Definition: it is inadequate thyroid hormone
production in newborn infants.
Causes:
1- iodine deficiency.
2- Thyroid gland is absent or
underdeveloped.
3-A hypoplastic gland may develop higher in
the neck or even
in the back of the tongue (lingual thyroid)
4- One common cause is the presence of
23. SYMPTOMS AND SIGNS
Infants born with congenital hypothyroidism
may show no effects, or may display mild
effects that often go unrecognized as a
problem.
1- excessive sleeping
2- reduced interest in nursing
3-, poor muscle tone
4- low or hoarse cry
5- infrequent bowel movements
6- exaggerated jaundice
24. DIAGNOSIS
In the developed world, nearly all cases of
congenital hypothyroidism are detected by
the newborn screening program.
These are based on measurement of TSH or
thyroxine (T4) on the second or third day of
life( Heel prick).
If the TSH is high, or the T4 low, the infant's
doctor and parents are called and a referral
to a pediatric endocrinologist is
recommended to confirm the diagnosis and
25. TREATMENT
The goal of newborn screening programs is
to detect and start treatment within the first
1–2 weeks of life. Treatment consists of a
daily dose of thyroxine, available as a small
tablet. The generic name is levothyroxine
The tablet is crushed and given to the infant
with a small amount of water or milk
Within a few weeks, the T4 and TSH levels
are rechecked to confirm that they are being
normalized by treatment
26.
27. CRETINISM
is an old term for the state of mental and
physical retardation.
Result from:
untreated congenital hypothyroidism
Iodine deficiency
28. CLINICAL PICTURE
1) Full picture of Hypothyroidism.
2) Growth Retardation.
A) PHYSICAL
Skeletal growth is more affected than soft
tissue growth
Long bones (linear growth) are more affected
than short bones
Disproportionate Dwarfism.
Delayed motor mile stones of development
(sitting, walking)
Delayed dentition + small teeth.
Delayed closure of fontanels.
29.
30.
31. B) MENTAL
Mental Retardation (permanent).
C) SEXUAL
Sexual retardation.
TREATMENT:
Replacement therapy (start very early).