hypo and hyperthyroidism causes , clinical finding diagnosis treatment

1. P R O F. D R . N A S E E R
H O D P A T H O L O G Y
THYROID
(HYPOTHYROIDISM)

2. HYPOTHYROIDISM
• It is a condition caused by structural or functional
derangement that interferes with the production of the
thyroid hormone.
• This is a common disorder.
• Prevalence increases with age.
• 10 folds more common in women than men.
• Defect may occur anywhere in hypothalamus – pituitary-
thyroid axis.

3. It is of two types:
• Primary (intrinsic abnormality in thyroid)
• Secondary (it is a result of pituitary and hypothalamus disease)
PRIMARY HYPOTHYROIDISM: can be,
1. congenital: it is a result of iodine deficiency in diet, other rare
forms include
* inborn error of metabolism that is any step leading to thyroid
hormone synthesis may be defective as ,
A. Iodine transport to thyrocytes for organification of iodine.
B. Binding of iodine to tyrosine residue of storage protein
thyroglobulin.
C. Iodotyrosine coupling to form hormonally active T3 and T4.
In rare stances complete absence of parenchyma (thyroid
agenesis)OR gland may be greatly reduced (hypoplasia).

4. 2. AUTO IMMUNE HYPOTHYROIDSM:
• Most common cause of hypothyroidism in iodine
sufficient areas of the world.
• Vast majority of cases of autoimmune hypothyroidism
are due to Hashimoto thyroiditis.
• Circulating auto antibodies including antimicrosomal
antithyroid peroxidase and antithyroglobulin antibodies
are found in this disorder.
• The thyroid is typically enlarged (goitrous).

5. 3. IOTROGENIC HYPOTHYROIDISM:
• It is caused by surgical or radiation induced ablation,
1. thyroidectomy for hyperthyroidism can lead to
hypothyroidism.
2. the gland can also be ablated by radiation by radio
iodine administration for the treatment of hypothyroidism
or exogenous irradiation such as external radiation
therapy to neck.
3. drugs given intentionally to decrease thyroid secretion
(for e.g methimezole and propylthiouracil can also cause
acquired hypothyroidism, agents use to treat non thyroid
condition for e.g lithium , p-amino salicylic acid can cause
hypothyroidism.)

6. 3. SECONDARY HYPOTHYROIDISM:
• Deficiency of TSH or TRH due to pituitary tumor of post
partum pituitary necrosis or trauma.
• hypothalamic damage from tumor, trauma or irradiation
therapy.

7. CRETINISM
• Refers to hypothyroidism that develops in infancy or early childhood.
• They are unfortunately mentally retarded.
• CLINICAL FEATURES:
• Impaired development of skeletal system and central nervous system
manifests severe mental retardation, short stature, coarse facial
features, protruding tongue and umbilical hernia.
• Mental retardation is related to thyroid deficiency in utero as T3 and T4
cross placenta is critical for fetal brain development.
• If maternal thyroid deficiency is before he development of fetal thyroid
gland , mental retardation is severe.
• While thyroid deficiency later in pregnancy after fetal thyroid is
functional does not effect normal brain development.

8. MYXEDEMA
• It develops in older child or adults.
• Myxedema is marked by,
• Slowing of physical and mental activity.
• Initial symptoms include generalized fatigue, apathy, mental
sluggishness.
• Speech and intellectual functions are slowed.
• Patient of myxedema are listless cold intolerant and frequently
overweight.
• Decrease sympathetic activity has constipation and decrease
sweating.
• Reduced cardiac output leads to shortness of breath and
decrease exercise capacity.
• In addition hypothyroidism promote atherogenic profile for e.g
increased in cholesterol and LDL levels contributes to increase
cardiovascular mortality.

9. • Histologically there is a increased accumulation of
glycosaminoglycan's and hyaluronic acid in subcutaneous
tissue of skin and other viscera results in non pitting
edema, broadening and coarsening of facial features.
• Enlargement of tongue and deepening of voice.
• Unexplained Increased in weight or hypocholesteremia
should be assessed for potential hypothyroidism.
• Measurement of TSH levels is the most sensitive screening
test for this disorder.
• TSH level is increased in primary hypothyroidism.
• TSH level is not increased in persons with hypothyroidism
due to primary hypothalamic or pituitary disease.
• T4 is decreased with individuals with hypothyroidism.

10. HYPERTHYROIDISM
. it is due to excessive release of thyroid hormone.
.THYROTOXICOSIS: it is a hypermetabolic state caused by elevated
circulating levels of T3 T4.
CAUSES:
Excessive release of pre form thyroid hormone in e.g thyroiditis or from
extra thyroid source.
PRIMARY HYPERTHYROIDISM : hyperthyroidism arising from intrinsic
thyroid abnormality.
SECONDARY HYPERTHYROIDISM: arising from process outside
thyroid as TSH secreting pituitary tumors.
Three most common causes of thyrotoxicosis are,
1. Diffuse hyperplasia. (graves disease responsible for 80 % cases)
2. Hyperfunction of multinodular goiter
3. Hyperfunctional thyroid adenoma.

11. CLINICAL COARSE:
• It is hypermetabolic state, induced excess thyroid hormone and over
activity of sympathetic nervous system.
• Excessive thyroid causes in crease in metabolic rate, ski tends to be
soft, warm, flushed due to increased blood flow and peripheral
vasodilation,
A. heat intolerance is common
B. sweating is increased
C. weight loss despite increase in appetite.
CARDIAC MANIFESTATION : are the most constant and earliest
feature.
• Elevated cardiac contractility and increased cardiac output as there
is increased peripheral oxygen requirement so,
A. tachycardia
B. palpitation
C. cardiomegaly
D. arrhythmias (atrial fibrillation is more common in elderly patient)
E. congestive heart failure.
THYROTOXIC CARDIOMYOPATHY: its reversible left ventricular
dysfunction leads to low cardiac output and heart failure.

12. OVERACTIVITY OF SYMPATHETIC NERVOUS
SYSTEM: produce,
A. tremors
B. hyperactivity
C .emotional liability
D .Anxiety
E. inability to concentrate
F. insomnia
Proximal muscle weakness and decrease muscle mass.
GIT DISTURBANCES, hyper motility, diarrhea and
malabsorption.

13. OCCULAR CHANGES: these changes often call attention to
hyperthyroidism.
A. wide staring gazed
B. lid lag due to sympathetic overs stimulation of superior
tarsals muscle.
C. proptosis (it occurs only graves disease)
SKELETAL SYSTEM : thyroid hormone stimulates bone
resorption results in,
• Osteoporosis with increased risk of fracture.
• Atrophy of skeletal muscle with fatty infiltrations.
• Minimal liver enlargement due to fatty infiltration.
• Generalized lymphoid hyperplasia and lymph adenopathy
in patient with graves disease.

14. THYROID STORM: It refers to abrupt onset of severe
hyperthyroidism,
• Occurs in patient with graves disease.
• Probably results from acute elevation of catecholamine's
during infections, surgery, cessation of ant thyroid drugs
or any stress .
• Patient id often febrile with tachycardia , out of proportion
of fever.
• Thyroid storm is a medical emergency, a significant
number of untreated patient die of arrhythmias.
APATHETIC HYPERTHYROIDISM:
• It refers to thyrotoxicosis in older adults in whom
comorbidities may blunt the features of hyperthyroidism.

15. DIAGNOSIS:
• TSH concentration is the most useful screening test for
hyperthyroidism.
• TSH levels are decreased even at the earliest stage.
• Confirm with the measurement of free T4 which is
increased.
SECONDARY HYPERTHYROIDISM:
(PITUITATRY ASSOCIATION)
• TSH levels are either normal or raised.
• TSH levels are determined after injection of thyrotropin
releasing hormone (TRH) is used.
• Normal rise in TSH after administration of TRH exclude
secondary hyperthyroidism.

16. • Once diagnosis of thyrotoxicosis is confirmed by TSH
assay and free thyroid hormone levels, measurement of
radioactive iodine uptake can determine the etiology.
1. diffuse increase uptake in whole gland means graves
disease.
2. increase uptake in solitary nodule indicates toxic
adenoma.
3. decrease uptake indicates thyroiditis.

17. THERAPEUTIC OPTIONS:
1. beta blockers to control the symptoms induced by
increased adrenergic tone.
2. Athionamide to block the new hormone synthesis.
3. iodine solutions to block the release of thyroid hormone.
4. thyroid hormones and agents that inhibit the peripheral
conversion of t4 to t3.
5. Radio iodine is incorporated to thyroid tissue resulting in
ablation of thyroid function over a period six to eighteen
weeks.

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