Thyroid gland
Hyperplasia / goiter
Endemic goiter

Author: Swati Satturwar, MBBS, M.D. (see Authors page)
Editor: F. Zahra Aly, M.D., Ph.D.

Revised: 29 September 2017, last major update September 2017

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Endemic goiter [title] "loattrfull text"[sb]
Cite this page: Satturwar, S. Endemic goiter. PathologyOutlines.com website. http://pathologyoutlines.com/topic/thyroidendemicgoiter.html. Accessed October 19th, 2017.
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-10 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 goiter

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
Microscopic (histologic) images

Images hosted on other servers:

Multinodular goiter

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
Board review 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 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.