Disorder of Thyroid Gland

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Disorder of Thyroid Gland

• Differential Diagnosis

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References

• Harrisons internal medicine
• Lange Pathophysiology
• Washington Manual
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• Stage of goiter
• Stage 0 no goiter
• Stage Ia goiter detectable only by palpation
  and not visible when the neck is fully extended
• Stage Ib goiter palpable and visible only when
  the neck is fully extended
• Stage II goiter visible with the neck in normal
  position
• Stage III very large goiter that can be
  recognized at a considerable distance.

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Overview of Thyroid Disease

• The clinician commonly encounters patients with
  one of five types of thyroid dysfunction
• (1) hyperthyroidism (thyrotoxicosis), caused by
  an excess of thyroid hormones
• (2) hypothyroidism (myxedema), caused by a
  deficiency of thyroid hormones
• (3) goiter, a diffuse enlargement of the thyroid
  gland, caused by prolonged elevation of TSH
• (4) thyroid nodule, a focal enlargement of a
  portion of the gland, caused by a benign or
  malignant neoplasm and
• (5) abnormal thyroid function tests in a
  clinically euthyroid patient.

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Pathogenesis of Thyroid Disorder

• Autoimmune processes
• stimulate the overproduction of thyroid hormones
  (thyrotoxicosis) or
• cause glandular destruction and hormone
  deficiency (hypothyroidism).
• benign nodules and various forms of thyroid
  cancer

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Pathogenesis-autoimmune process

• sensitization of the host's own lymphocytes to
  various thyroidal antigens.
• Three major thyroidal antigens have been
  documented
• thyroglobulin (Tg),
• thyroidal peroxidase (TPO),
• TSH receptor.
• ExampleIn Graves' disease, the TSH receptor
  autoantibody TSH-R stim Ab stimulates the
  thyroid follicular cells to produce excessive
  amounts of T4 and T3.

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Antibody? Adenoma? Ectopic Secretion?
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Autoimmune thyroiditis

• Hashimotos thyroiditis
• marked lymphocytic infiltration of the thyroid
  with germinal center formation
• atrophy of the thyroid follicles accompanied by
  oxyphil metaplasia, absence of colloid, mild to
  moderate fibrosis.
• Atrophic thyroiditis
• the fibrosis is much more extensive,
• lymphocyte infiltration is less pronounced,
• thyroid follicles are almost completely absent.
• Atrophic thyroiditis likely represents the end
  stage of Hashimoto's thyroiditis rather than a
  distinct disorder.

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Terminology

• Thyrotoxicosis the state of thyroid hormone
  excess
• Hyperthyroidism the result of excessive thyroid
  function.
• However, the major etiologies of thyrotoxicosis
  are hyperthyroidism caused by Graves' disease,
  toxic multinodular goiter, and toxic adenomas.

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Thyroid function tests

• Thyroid function tests
• TSH T3 T4 RT3U FTI
  Free T4
• Antimicrosome AB (Anti-peroxidase AB) (TPO AB)
• Antithyroglobulin AB
• TSH receptor AB
• thyroglobulin

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• Best initial diagnostic test Plasma TSH
• Free T4 and Free T3 p.s.T3(total T3?total
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• Autoantibodies
• Anti-thyroglobulin antibodies
• Antithyroid microsomal/thyroid peroxidase
  antibodies(TPO)
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• TSH receptor Ab -Graves disease?specific?Ab

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Lab testHyperthyroidism

• Serum thyroid hormones are elevated.
• Both the free thyroxine (FT4) and the free
  thyroxine index (FT4I) are elevated.
• In 510 of patients, T4 secretion is normal
  while T3 levels are high (so-called T3 toxicosis
• Hyperthyroidism resulting from Graves' disease
  suppressed serum TSH level
• However, TSH levels may also be suppressed in
  some acute psychiatric and other nonthyroidal
  illnesses.
• In the rare TSH-secreting pituitary adenomas
  (so-called secondary hyperthyroidism) and in
  hypothalamic disease with excessive TRH
  production (so-called tertiary hyperthyroidism),
  hyperthyroidism is accompanied by elevated plasma
  TSH.
• The radioactive iodine (RAI) uptake of the
  thyroid gland at 4, 6, or 24 h
• increased when the gland produces an excess of
  hormone (eg, Graves' disease)
• decreased when the gland is leaking stored
  hormone (eg, thyroiditis),
• when hormone is produced elsewhere (eg, struma
  ovarii), and when excessive exogenous thyroid
  hormone is being ingested (eg, factitious
  hyperthyroidism). Technetium 99m scanning can
  provide information similar to that obtained with
  RAI and is quicker and entails less radiation
  exposure.
• The TRH test is sometimes helpful in diagnosis
  when patients have confusing results of thyroid
  function tests. In normal individuals,
  administration of TRH (500 g intravenously)
  produces an increase in serum TSH of at least 6
  mU/L within 1530 min. In primary
  hyperthyroidism, TSH levels are low and TRH
  administration induces little or no rise in the
  TSH level.

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Flow chart of Hyperthyroidism D.D.
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Flow chart of Hypothyroidism D.D.
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Features of Graves Disease

• 6080 of thyrotoxicosis, women predominate,
  2050 y/o
• Ophthalmopathy / Proptosis (06)
• Pretibial myxedema

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