Thyroid & parathyroid

Hyperplasia / goiter

Endemic goiter



Topic Completed: 1 September 2017

Minor changes: 2 June 2021

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PubMed Search: Endemic goiter [title] "loattrfull text"[sb]

Swati Satturwar, M.D.
F. Zahra Aly, M.D., Ph.D.
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Cite this page: Aly F, Satturwar S. Endemic goiter. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/thyroidendemicgoiter.html. Accessed December 7th, 2021.
Definition / general
  • Defined as thyroid enlargement due to iodine deficiency, primarily dietary deficiency
  • Endemic goiter term is used when the local prevalence is greater than 5 - 10%
  • Common in mountainous and iodine deficient areas of the world where the diet contains insufficient amount of iodine
  • Iodine supplementation reduces frequency of goiter but may increase prevalence of autoimmunity (Hormones (Athens) 2007;6:25) and follicular neoplasm
  • May be exacerbated by goitrogens, such as cassava and cruciferous vegetables or sewage contamination of water
  • May also be due to high iodine intake (Am J Public Health 2000;90:1633)
  • Cretinism: severely stunted physical and mental growth due to untreated congenital deficiency of thyroid hormone secondary to maternal hypothyroidism; may be due to iodine deficiency in pregnancy or selenium deficiency
Essential features
  • Diffuse goiter is followed by nodular goiter and autonomous nodule formation upon iodine supplementation
  • Generally due to dietary deficiency of iodine due to low content of iodine in soil or water
  • Other factors include exposure to goitrogens
Terminology
  • Iodine deficiency related thyroid goiter
ICD coding
Epidemiology
Sites
  • Global involvement of thyroid gland
Pathophysiology
  • Iodine is required for thyroid hormone synthesis
    • When there is nutritional deficiency of iodine, there is decreased capacity of the thyroid gland to produce thyroid hormones
    • Due to the negative feedback, there is increased secretion of TSH by hypothalamus
    • Increased TSH results in diffuse¬†hypertrophy¬†of thyroid glandular tissue which manifests grossly as a goiter
  • Euthyroidism is maintained with iodine intake levels of 150 - 200 ug/day and 250 ug/day during pregnancy and puberty
  • Not everyone in endemic area will have a goiter, due to variation in utilization of iodine, renal clearance of iodide or ratio of T3 (more metabolically potent) to T4
Etiology
  • Dietary deficiency of iodine
  • May be exacerbated by goitrogens, such as cassava and cruciferous vegetables or sewage contamination of water
Clinical features
  • Thyroid enlargement (goiter)
  • Hypothyroidism due to decreased production of T3 & T4 hormones
  • Hyperthyroidism
  • Compression of trachea and esophagus
Diagnosis
  • Clinical examination by palpation to assess thyroid enlargement
  • Ultrasonography
  • Serum T3, T4 and TSH
  • Urinary iodine levels
Laboratory
  • Increased TSH and decreased T3 & T4
  • Urine iodine level decreased (mild: 50 - 99 ug/l, moderate 20 - 49 ug/l and severe: < 20 ug/l)
Radiology description
  • Ultrasound: estimation of thyroid volume, isoechoeic nodules with cystic changes, hemorrhage or calcification
  • For adults, upper limit of volume is 25 ml (men), 18 ml (women), 16 ml (children aged 5 yrs) and 5 ml for children aged 6 yrs
Treatment
  • Supplemental iodine in the form of tablets, iodinated salt / oil / water / bread is effective in prevention
  • Treatment for established goiter is thyroxine; , iodine is contraindicated
  • Surgery only for pressure symptoms or autonomous nodules
Clinical images

Images hosted on other servers:

Endemic multinodular goiter

Gross description
  • Diffuse enlargement initially, progresses to multiple nodules, degenerative cystic changes, fibrosis, old and new hemorrhage (similar to multinodular goiter)
Gross images

Images hosted on other servers:

Endemic multinodular goiter

Microscopic (histologic) description
  • Follicles of varying size, flat / effaced follicular cells, cysts, hemorrhage or calcification
  • Follicular adenoma
  • Lymphocytic infiltrate
Cytology description
  • Follicular cells arranged in monolayered, honeycomb-like sheets, with delicate cytoplasm and indistinct cytoplasmic borders
  • Round to oval monomorphic nuclei and finely granular chromatin and absent nucleoli
  • Rare microfollicles
  • Abundant colloid
Cytology images

Contributed by Ayana Suzuki, C.T.

Watery colloid

Cracking colloid

Follicular clusters

3D structures

Paravacuolar granules

Board review style question #1
Which statement regarding endemic goiter is false?

  1. Increases risk for follicular neoplasm
  2. Increases risk for papillary neoplasm
  3. May cause tracheal compression
  4. Most common cause is dietary deficiency of iodine
Board review style answer #1
B. Endemic goiter increases the risk of follicular neoplasm and anaplastic carcinoma. On the contrary, papillary neoplasms occur more in iodine sufficient areas.

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