Hypothyroidism

Dr .Amal Awad Abbas

Objectives
1- Define hypothyroidism
2- Outline the causes of hypothyroidism
3- Classify hypothyroidism
4- Recognize the clinical feather of
hypothyroidism
5- Outline investigation of hypothyroidism
6- Manage patient with hypothyroidism
Hypothyroidism
Is diagnosed by a decreased serum free T4 and may
be as the result of :
1-disease of thyroid gland (primary hypothyroidism)
2-abnormalities of pituitary gland (secondary)
3-abnormalities of hypothalamus (tertiary)

Hypothyroidism is a congenital or acquired and may

be associated with a goiter.
Congenital hypothyroidism
Congenital hypothyroidism occur in
approximately 1 in 2000 to 4000 live birth and
is caused by dysgenesis (agenesis ,aplasia
,ectopia) or less often ,dyshormonogenesis
(eg: enzyme defects)
Clinical manifestation :
Most infant with congenital hypothyroidism are
asymptomatic at birth , even if there is complete
agenesis of thyroid gland
This situation is attributed to the transplacental
passage of moderate amount of maternal T4 which
provides fetal levels that are approximately 33% of
normal at birth
Despite this maternal contribuation of thyroxine
,hypothyroid infant still have a low few serum
T4 and elevated TSH level and so will be
identified by newborn screening programs.
The clinician depend on neonatal screening tests for
the diagnosis of congenital hypothyroidism
(laboratory errors occur and
awareness of early symptom and
signs must be maintained )
1- birth weight and length are normal, but head size
may be slightly increased because of myxedema of
the brain
2-prolongation of physiological jaundice caused by
delayed maturation of glucuronide conjugation ,may
be the earliest sign .
3-feeding diffuculities especially sluggishness, lack of
interest ,somnolence and
4-choking spells during nursing are often present
during the 1st month of life .
5-Respiratory difuculties ,due in part to the large tongue
,include apneic episodes ,noisy respirations and nasal
obstruction
Typically ,respiratory distress syndrome also occurs .
6-affected infants cry little ,sleep much ,have poor
appetite and are generaly sluggish .there may be
constipation that does not usually respond to treatment .
7-The abdomen is large ,and an umblical hernia is
usually present
8-the temperature is subnormal often < 35 c
9-the skin ,of the extremities ,may be cold and
mottled .edema of the genitals and extremities may
be present .
10-The pulse is slow and heart murmurs
,cardiomegaly and asymptomatic pericardial
effusion are commom
11-Macrocytic anemia is ofen present and is
referactory to treatment with hematinics.
Approximately 10%of infant with congenital
hypothyroidism have associated congenital
anomalies .
Cardiac anomalies are most common
Anomalies of nervous system and eye have also been
reported ,
Infant with congenital hypothyroidism may have
associated hearing loss.
Child’s growth will be stunted
Extremities are short ,head size is normal or even increased .
Anterior and posterior fontanels are open widely ,
Observation of this sign at birth can serve as an intial clue to
the early recognition of congenital hypothyroidism
The eyes appear far apart and the bridge of the broad nose is
depressed .the palpebral fissure are narrow and the eyelids
are swollen .
The mouth is kept open and the the thick broad tongue
protrudes . Dentition will be delayed .
The neck is short and thick and there may be deposits of fat
above the clavicle and between the neck and shoulders .
Hands are broad and the fingers are short .
Skin is dry and scaly and general pallor .
Myxedema is manifested particularly in the skin of
the eyelids ,the back of the hands ,and genitals .
Carotenemia can cause ayellow discoloration of the
skin but the sclera remain white .
Scalp is thickened
Hair is coarse ,brittle and scanty .
Development
Is usually delayed .hypothyroid infants appear
lethargic and are late in learning to sit and stand .
The voice is hoarse and they don’t learn talk .
The degree of physical and mental retardation
increase with age
Sexual maturation may be delayed or might not take
place at all .
The muscles are usually hypotonic .
Treatment
With levothyroxine is intiated with in 1 month or less
after birth
Screenning programs usually offer therapy with in 1
to 2 weeks of birth
The dose of levothyroxine changes with age
10 to 15 µg/kg of levothyroxine is used for newborn
But about 3 µg/kg is used later in childhood
The prognosis for normal intellectual development
is excellent .
Acquired hypothyroidism
The clinical manifestations may be subtle
hypothyroidism should be suspected in any child
who has decline in growth velocity , especially if not
associated with weight loss . The most common
cause of acquired hypothyroidism in older children is
lymphocytic autoimmune thyroiditis (hashimoto
thyroiditis )
In many areas of the world , iodine deficiency is the
etiology of endemic goiter (endemic cretinism)
Hashimoto thyroiditis
Also known as autoimmune or lymphocytic
thyroiditis
Hashimoto thyroiditis is a common cause of goiter
and acquired thyroid disease in older children and
adolescent
A family history of thyroid disease is present
In 25% to 35% of patients.
Clinical manifestation
Include a firm ,non tender euthyroid
Onset typically occurs after 6 years of age with a
peak incidence in adolescence .
With a female predominance
Associated autoimmune diseases include diabetius
mellitus type 1 ,adrenal insufficiency
and hypoparathyroidism.
The diagnosis may be confirmed by serm antithyroid
peroxidase (previously antimicrosomal and
antithyroglobulin antibodies )
Treatment with thyroid hormone is sufficient to
normalize TSH and free T4 is indicated for
hypothyroidism in Hashimoto thyroiditis
Patients without manifestation of hypothyroidism require
thyroid function testing (serum TSH and free T4) every 6
to 12 months to detect the later development of
hypothyroidism
Goiter with a normal TSH usually is not an indication for
treatment
Congenital hypothyroidism
A- absence of distal femoral epiphysis in a 3 months old infant who was born at term .
This is evidence for the onset of the hypothyroid state during fetal life
B-epiphyseal dysgenesis in the head of the humerus in the 9 yr old girl who had been
inadequately treated with thyroid hormone .