HYPOTHYROIDISM

1. Hypothyroidism.
Introduction.
• Decreased secretion of thyroid hormones is called
Hypothyroidism.
• If hypothyroidism occurs in infants is called Cretinism.
• If hypothyroidism occurs in adults is called Myxedema.
Causes of hypothyroidism.
Primary Causes.
a) Congenital.
b) Defects of hormone of synthesis.
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2. c) Autoimmune.
d) Post-surgery.
e) Tumor of the thyroid gland.
Secondary Causes.
– Hypopituitarism.
– Isolated THS deficiency.
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3. Cretinism.
It is occurs in infants or children.
Causes of Cretinism.
Cretinism occurs due to congenital absence of thyroid
gland, genetic disorder or lack of iodine in the diet.
Signs of cretinism in infants.
A neonate without a thyroid gland may have normal
appearance and function b/c it was supplied with some
thyroid hormone by the mother in intra uterine life.
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4. But a few weeks after birth, the neonate
movements become sluggish and both
physical and mental growth begin to be
greatly retarded, causing
1) Unproportional and restricted growth.
2) Mental retardation.
3) Tongue is enlarged, so there may be
difficulty in swallowing.
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5. 4) Sexual characters do not develop.
5) Bones are short and muscle mass is
decreased.
Treatment.
– Iodine.
– Thyroxine.
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6. Myxedema.
It is occurs in adults.
Causes for myxedema.
• Myxedema occurs due to diseases of
thyroid gland, genetic disorder or iodine
deficiency.
• Deficiency of THS or thyrotropic
releasing hormone.
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7. • The common cause of myxedema is the
autoimmune disease called Hashimoto`s
thyroiditis which is common in late middle
aged women.
• In most of the patients it starts with
glandular inflammation called thyroiditis
caused by autoimmune antibodies.
• Later it leads to destruction of the gland.
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8. Signs and symptoms of Myxedema.
– Development of edematous appearance throughout
the body.
– It is associated with following symptoms.
– Swelling of face.
– Bagginess under the eyes.
Atherosclerosis:
(Hardening of the walls of arteries b/c of fat
deposits and other substances)
In myxedema it occurs b/c of increased plasma
level of cholesterol.
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9. Other general features of hypothyroidism
in adults are.
– Anemia.
– Fatigue.
– Increase body weight.
– Constipation.
– Mental sluggishness.
– Muscular sluggishness.
– Depressed hair growth.
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10. Goiter.
• Goiter means enlargement of the thyroid gland.
• It occurs both in hypothyroidism and
hyperthyroidism.
Goiter in Hyperthyroidism (Toxic Goiter)
• Toxic goiter is the enlargement of thyroid gland
with increased secretion of thyroid hormones
caused by thyroid tumor.
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11. Goiter in hypothyroidism
(Nontoxic Goiter)
• Nontoxic goiter is the enlargement of thyroid
gland without increase in hormone secretion. It
is also called hypothyroid goiter.
Types.
• Endemic Colloid Goiter.
• Idiopathic nontoxic Goiter.
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12. Endemic Colloid Goiter.
• It caused by iodine deficiency. Found especially
in persons living in the areas where there is lack
of iodine in soil and water.
• Iodine deficiency occurs when intake is less than
50 ug/day.
Mechanism of Development.
• Lack of iodine prevents production of both T3
and T4,but does not stop the formation of
thyroglobulin (inhibitor of TSH secretion)
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13. • As a result, no hormone is available to
inhibit production of TSH by the anterior
pituitary, this allows the pituitary to secrete
excessively large amount of TSH.
• The TSH then causes the thyroid cells to
secrete tremendous amounts of
thyroglobulin into the follicles, and the
gland grows larger and larger.
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14. Idiopathic Nontoxic Goiter.
• It caused by inflammation of the thyroid gland
(Thyroiditis).
• It also caused by abnormality of enzyme system
required for the formation of the thyroid
hormone.The lack of enzymes may cause
1- Deficient iodide-trapping mechanism.
2- Deficient peroxidase system.
3- Deficiency of coupling of iodinated tyrosines
in the thyroglobulin molecule.
4- Deficiency of the deiodinase enzyme.
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15. • All these defects leads to iodine deficiency
and goiter formation.
Mechanism of Development.
• Thyroiditis causes slight hypothyroidism,
which then leads to increased TSH
secretion and progressive growth of non
inflamed portion of the gland.
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16. • This could explain why these glands usually are
nodular,with some portions of the gland growing
while other portions are being destroyed by
thyroiditis.
• Some foods contain goitrogenic substances that
have a propyl thiouracil–type of anti thyroid
activity, thus also leading to TSH-stimulated
enlargement of the thyroid gland. Sush
goitrogenic substances are found in some
varieties of turnips and cabbages.
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