1.
Thyroid disorders
haimanot c.(MD)

2.
Disease of the Thyroid
content
• Fetal development
• Thyroid physiology
• Thyroid regulation
• Thyroid hormone studies
• Hypothyroidism
• Hyperthyroidism
• Thyroid carcinoma

3.
Fetal thyroid development
The fetal thyroid arises from an outpoaching
of the foregut at the base of tongue.
Around 8-10wks of gestation it migrates to its
normal location over the thyroid cartilage.
Characteristic thyroid follicle cell and colloid
formation is seen by wk 10.

4.
T4 and lesser extent of T3 synthesis and
secretion occurs starting from wk 12.
 Maturation of H-P-T axis occurs over 2nd half
of pregnancy, normal feedback mechanism
starts after 3mo postnatal.

5.
Thyroid physiology
Main function- to synthesize thyroid hormone(T4
and T3)
And the only physiologic role of iodine(iodized
form) is in the synthesis of these hormones.
Recommended dietary intake:
-infant 30µg/kg/24hrs
-chidren 90-120µg/24hrs
-adult 150µg/24hrs

6.
Thyroid tissue has an avidity for iodine to trap,
transport and concentrate in the follicular
lumen for the synthesis of hormones.
Then entry of iodide from the circulation in to
the thyroid is carried out by sodium iodide
symporter.
Then diffuses to the colloid via pedrin.

7.
• Before trapped iodide can react with tyrosine,
it must be iodized by the help of thyroidal
peroxidase.
• Thyroid cells produces thyroglobulin (large
molecular weight gp) which contains around
150 units of tyrosine.

8.
Then iodination of tyrosine forms
monoiodotyrosine and diiodotyrosine and
then coupling takes place to form T4 and T3.
Once formed, stored as thyroglobulin in
colloid until ready to body cells then liberated
by activation of proteases and peptides.

9.
The metabolic potency of T3 is 3-4times that
T4.
And also T3 is physiologically active hormone.
Only 20% of T3 is secreted by the thyroid.
The remaining produced by deiodination of T4
in liver , kidney, and other extra thyroidal
tissues by type I 5’ deiodinases

10.
Thyroid hormone:
- Increases oxygen consumption
- Stimulate protien synthesis
-Influence growth and differentiation
- Affect carbohydrate, lipid, and vit.
metabolism

11.
Thyroid Regulation
 In states of decreased production of thyroid
hormone, TSH and TRH are increased.
 Exogenous thyroid hormone or increased
thyroid hormone synthesis inhibits TSH and
TRH production.
 Except in the neonate, levels of TRH in serum
are very low.

12.
+
+
-
- Synthesize TRH by
6-8th week
Secrete TSH
by 12th week
Feedback mechanism
starts by 3rd month

13.
THYROID HORMONE STUDIES
Serum thyroid hormone(T3,T4 both total and
free)
Serum TSH level(sensitive indicator for p.
hypothyroidism)
Serum TBG(can be affected by different
factors)
Age should be considered in hormone
determination.

14.
Other studies that contribute for diagnosis:
-Radionuclide studies
-Ultrasonographic studies

15.
HYPOTHYROIDISM HYPERTHYROIDISM
DECREASED
PRODUCTION
INCREASED
PRODUCTION

16.
Hypothyroidism
Hypothyroidism results from deficient
production of thyroid hormone or a defect in
thyroid hormone receptor activity .
 congenital or acquired .

17.
CONGENITALHYPOTHYROIDISM
 Most cases of congenital hypothyroidism are
not hereditary and result from thyroid
dysgenesis.
 Some cases may be familial, usually caused
by one of the inborn errors of thyroid
hormone synthesis, and may be associated
with a goiter.

18.
In many cases, the deficiency of thyroid
hormone is severe, and symptoms develop in
the early weeks of life.
In others, lesser degrees of deficiency occur,
and manifestations may be delayed for
months.

19.
EPIDEMIOLOGY
• The prevalence of congenital hypothyroidism
based on neonatal screening is 1/4,000 infants
worldwide;
• Prevalence is lower in black Americans
(1/32,000) and higher in Hispanics and Native
Americans (1/2,000).
• F:M = 2:1

20.
ETIOLOGY(primary or central)
PRIMARY:
1.DYSGENESIS -the most common cause of
permanent congenital hypothyroidism around
80%-85 (aplasia 33%, hypoplasia or
ectopic(66%)).
Most causes are unknown and sporadic
8-10% familial (thyroglossal cyst and
hemiagenesis in 1st degree relatives support
some genetic defect.

21.
2.DYSHORMONOGENESIS-The problem is in TH
synthesis
15% of cases detected by neonatal screening
programs.
when the defect is incomplete ,compensation
occurs, and the manifestation of is delayed.
Goiter is almost always present.

22.
3.TSH unresponsiveness
4.Defect in thyroid hormone transport
5.Resistance to thyroid hormone
6.Maternal antibodies: thyrotropin receptor–
blocking antibody
7.Iodine deficiency (endemic goiter)
8.Maternal medications

23.
CLINICAL MANIFESTATIONS
Asymptomatic at birth even in case of
agenesis
birth wt and length normal but head size may
be slightly increased
Prolonged physiologic jaundice, delayed
passage of stool

24.
 Feeding difficulties, especially sluggishness,
lack of interest, somnolence, and choking
spells during nursing, are often present
during the 1st mo of life.
 Respiratory difficulties, due in part to the
large tongue, include apneic episodes, noisy
respirations, and nasal obstruction.
 Affected infants cry little, sleep much, have
poor appetites, and are generally sluggish.

25.
 There may be constipation that does not
usually respond to treatment.
 The abdomen is large, and an umbilical
hernia is usually present.
 The temperature is subnormal, often less
than 35°C (95°F), and the skin, particularly
that of the extremities, may be cold and
mottled.
 Edema of the genitals and extremities may
be present.

26.
– Macroglossia
– Large fontanelles (anterior
and posterior)
– Umbilical hernia
– Mottled, rough or dry skin
– Developmental delay
– Pallor, hypothermia
– Myxedema
– Chocking during feeding.

27.
The pulse is slow, and heart murmurs,
cardiomegaly, and asymptomatic pericardial
effusion are common.
Macrocytic anemia is often present and is
refractory to treatment.
 Because symptoms appear gradually, the
clinical diagnosis is often delayed.
Approximately 10% of infants with congenital
hypothyroidism have associated congenital
anomalies.

28.
 Cardiac anomalies are most common, but
anomalies of the nervous system and eye
have also been reported.
 If congenital hypothyroidism goes
undetected and untreated, these
manifestations progress.
 Retardation of physical and mental
development becomes greater during the
following months, and by 3–6 mo of age the
clinical picture is fully developed .

29.
 partial deficiency of thyroid hormone, the
symptoms milder, the syndrome incomplete,
and the onset delayed.
 Although breast milk contains significant
amounts of thyroid hormones, particularly
T3, it is inadequate to protect the breast-fed
infant with congenital hypothyroidism, and it
has no effect on neonatal thyroid screening
tests.

30.
 stunted, the extremities are short, and the
head size is normal or even increased.
 The anterior and posterior fontanels are open
wide. Myxedema is manifested, in the
eyelids, the back of the hands, and the
external genitals.
The skin shows general pallor.
Thickened scalp, and the hair is coarse, brittle,
and scanty and hairline reaches far down on
the forehead appears wrinkled.

31.
Development is usually retarded.
appear lethargic and are late in learning to sit
and stand.
The voice is hoarse, and they do not learn to
talk.
The degree of physical and mental retardation
increases with age.
Sexual maturation may be delayed or may not
take place at all.

32.
The muscles are usually hypotonic, but in rare
instances generalized muscular
pseudohypertrophy occurs.

33.
LABORATORY
 T4 ,when T4 is low do TSH
 Scintigraphy can help to pinpoint the
underlying causes in infants with congenital
hypothyroidism
 ECG – low voltage P and T waves with
diminished QRS complex due to poor LV
function and pericardial effusion.

34.
Primary/Central Hypothyroidism
Hallmark of primary hypothyroidism
*Serum T4 is LOW and TSH is elevated
• Hall mark of central Hypothyroidism
(Hypothalamus/pitutary)
*Serum T4 and TSH levels are low

35.
TREATMENT
 Na L-thyroxine given Po is the Rx of choice.
dose - neonates 10-15 µg/kg
children 4 µg/kg

36.
PROGNOSIS
 Early diagnosis and treatment from the first
week of life has good prognosis.
 Delay in diagnosis ,inadequate treatment and
poor compliance will result in variable brain
damage.