The document discusses thyroid hormone disorders. It begins by describing the thyroid gland and its hormones. The thyroid regulates metabolism through thyroid stimulating hormone and secretes thyroid hormones T3 and T4. Hypothyroidism occurs when thyroid hormone production is inadequate, while hyperthyroidism is excessive thyroid hormone release. Common causes of hypothyroidism include Hashimoto's thyroiditis and thyroid removal. Graves' disease and toxic adenomas are common causes of hyperthyroidism. Laboratory tests can distinguish between hypo- and hyperthyroid states based on TSH, T3 and T4 levels.

1. THYROID HORMONE
DISORDERS
AMAL GEORGE
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2. THYROID GLAND
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 Butterfly-shaped endocrine gland.
 Second largest endocrine gland in the body
 Weighs about 30g in adults.
 Principle hormones : T3, T4 &reverse T3.
 It also secrete calcitonin

3. FUNCTIONS
 Stimulation and maintenance of metabolic process
 Produces
 Thyroid stimulating hormone (TSH), produced by the pituitary gland, acts
to stimulate hormone production by the thyroid gland.
 Secretes Calcitonin which regulates levels of calcium and phosphate in
the blood
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Triiodothyronine (T3)
Thyroxine (T4)

4. HORMONES
 Two principal hormones
 Thyroxine (T4 ) and triiodothyronine (T3)
 Required for homeostasis of all cells
 Influence cell differentiation, growth, and metabolism
 Considered the major metabolic hormones because they target virtually every tissue
 Regulates thyroid hormone production, secretion, and growth
 Is regulated by the negative feedback action of T4 and T3
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Thyroid-Stimulating Hormone (TSH)

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 T4 is the primary secretory
product of the thyroid
gland, which is the only
source of T4
 The thyroid secretes
approximately 70-90 g of
T4 per day
 T3 is derived from 2 processes
 The total daily production rate
of T3 is about 15-30 g
 About 80% of circulating T3
comesfrom de iodination of T4
in peripheral tissues
 About 20% comes from direct
thyroid secretion
T4 T3

6. Hypothalamic-Pituitary-Thyroid Axis
Negative Feedback Mechanism
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7.  Disorders of the thyroid are common and consist of 2 general presentations:
changes in the size or shape of the gland or changes in secretion of
hormones from the gland.
 Hypothyroidism refers to the inadequate production of thyroid hormone or
diminished stimulation of the thyroid by TSH
 Hyperthyroidism refers to those conditions in which thyroid hormones are
excessively released due to gland hyper function.
Over view of Disorders
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8. Thyroid Disease Spectrum
TSH T4 T3
Hypothyroidism High Low Low
Hyperthyroidism Low High High
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Overt Hypothyroidism
TSH >4.7 IU/mL, Free T4 Low
Subclinical Hypothyroidism
TSH >4.7 IU/mL, Free T4 Normal
Euthyroid
TSH 0.5-4.7 IU/mL, Free T4 Normal
Hyperthyroidism
TSH <0.5 IU/mL, Free T3/T4 Normal or Elevated

9. Hypothyroidism
 Hashimoto's thyroiditis : In this autoimmune disorder, the body attacks
thyroid tissue. The tissue eventually dies and stops producing hormones.
 Removal of the thyroid gland: The thyroid may have been surgically
removed or chemically destroyed.
 Exposure to excessive amounts of iodide: Cold and sinus medicines,
the heart medicine amiodarone, or certain contrast dyes given before
some X-rays may expose you to too much iodine. You may be at greater
risk for developing hypothyroidism if you have had thyroid problems in
the past.
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10.  Primary hypothyroidism
 From thyroid destruction
 Central or secondary hypothyroidism
 From deficient TSH secretion, generally due to sellar lesions such as pituitary
tumor or craniopharyngioma
 Infrequently is congenital
 Central or tertiary hypothyroidism
 From deficient TSH stimulation above level of pituitary—ie, lesions of
pituitary stalk or hypothalamus
 Is much less common than secondary hypothyroidism
Hypothyroidism: Types
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11.  Congenital hypothyroidism
 Agenesis of thyroid
 Defective thyroid hormone biosynthesis due to enzymatic defect
 Thyroid tissue destruction as a result of
 Chronic autoimmune (Hashimoto) thyroiditis
 Radiation (usually radioactive iodine treatment for thyrotoxicosis)
 Thyroidectomy
 Other infiltrative diseases of thyroid (eg, hemochromatosis)
 Drugs with antithyroid actions (eg, lithium, iodine, iodine-containing drugs,
radiographic contrast agents, interferon alpha)
Primary Hypothyroidism:
Underlying Causes
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12. Hyperthyroidism
 Graves' disease: The production of too much thyroid hormone.
 Toxic adenomas: Nodules develop in the thyroid gland and begin to
secrete thyroid hormones, upsetting the body's chemical balance; some
goiters may contain several of these nodules.
 Subacute thyroiditis: Inflammation of the thyroid that causes the gland to
"leak" excess hormones, resulting in temporary hyperthyroidism that
generally lasts a few weeks but may persist for months.
 Pituitary gland malfunctions or cancerous growths in the thyroid gland:
Although rare, hyperthyroidism can also develop from these causes.
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13. Hypothyroidism Hyperthyroidism
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