Goiter pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:

Overview

When the TRH-TSH thyroid hormone axis is interfered, it results in the structural and functional changes of the thyroid gland. Increased TSH production is trigerred by a deficiency in thyroid hormone synthesis or intake. In order to normalize thyroid hormone levels, the increase in TSH leads to increased cellularity and hyperplasia of the thyroid gland and when this process is continuous, it leads to goiter.

Pathophysiology

Pathogenesis

• Goiters may can occur as a result of either hypothyroidism, hyperthyroidism, or when the levels of thyroid hormone are normal.
• Thyroid enlargement (goiter) and hypothyroidism may occur due to compensatory responses as a result of a severe underlying disorder.
• When the thyroid gland can't secrete enough thyroid hormone to cater to the metabolic requirements, it may lead to simple goiter.
• In order to compensate for inadequate hormone synthesis the thyroid gland enlarges, this type of compensation overcomes mild to moderate hormonal impairment.
• When the TRH-TSH thyroid hormone axis is interfered, it results in the structural and functional changes of the thyroid gland.
• Increased TSH production is trigerred by a deficiency in thyroid hormone synthesis or intake.
• In order to normalize thyroid hormone levels, the increase in TSH leads to increased cellularity and hyperplasia of the thyroid gland and when this process is continuous, it leads to goiter.
• Thyroid hormone deficiency may be related to iodine deficiency, inborn errors of thyroid hormone synthesis and goitrogens.
• Goiters may from as a result of a many TSH receptor agonists. The TSH receptor gets stimulated under the following conditions:
  • Adenoma of the pituitary
  • Adenoma of the hypothalamus
  • Pituitary resistance to thyroid hormone
  • TSH receptor antibodies
  • Tumors producing hCG (human chorionic gonadotropin)

• The pathophysiological consequences of goitres results from one of the following:
  • The effect of thyroid hormone dysfunction
  • The effect of enlarged thyroid gland
  • The effect of primary disease causing goitre

• The effect of thyroid hormone dysfunction:
  • Thyroid hyperfunction (hyperthyroidism) → Features of hyperthyroidism
  • Thyroid hypofunction (hypothyroidism) → Features of hypothyroidism

• The effect of enlarged thyroid gland:
  • Effect on the trachea → dyspnea
  • Effect on the esophagus → dysphagia
  • Effect on the superior venacava → distended neck veins
  • Effect on the recurrent laryngeal nerve → horsiness of voice

• The effect of primary disease causing goitre:
  • The effect depends on the underlying disease

Genetics

• Goiter may be caused by a mutation in the following genes which vary from one family to the other:

• Thyroglobulin (Tg) gene
• Thyroid-stimulating hormone receptor (TSHR) gene
• Na+/I- symporter (NIS) gene

Gross Pathology

• On gross pathology, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].

By Ed Uthman from Houston, TX, USA (Thyroid, Diffuse Hyperplasia) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

Microscopic Pathology

Microscopic studies that aid in the histopathological analysis:

• Fine needle aspiration cytology (FNAC)
• Open biopsy

• On microscopic histopathological analysis, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].