Thyroid & parathyroid
Hyperplasia / goiter
Endemic goiter
Last author update: 1 September 2017
Last staff update: 28 August 2023
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Table of Contents
Definition / general | Essential features | Terminology | ICD coding | Epidemiology | Sites | Pathophysiology | Etiology | Clinical features | Diagnosis | Laboratory | Radiology description | Treatment | Clinical images | Gross description | Gross images | Microscopic (histologic) description | Cytology description | Cytology images | Additional references | Board review style question #1 | Board review style answer #1Cite this page: Aly F, Satturwar S. Endemic goiter. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/thyroidendemicgoiter.html. Accessed December 2nd, 2024.
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
- Over 1/3 of world population live in iodine deficient area; 1.6 billion are at risk of iodine deficiency; 655 million have goiter
- Prevalence of endemic goiter can be artificially increased if the normal upper limit of thyroid volume is decreased
- Still present in mountainous districts of Alps, Andes or Himalayas, Bulgaria (Biol Trace Elem Res 2007;116:273), India (Indian J Med Res 2008;128:601), Russia (Georgian Med News 2005;126:67), Spain (An Pediatr (Barc) 2006;65:234), Turkey (Exp Clin Endocrinol Diabetes 2009;117:64), Egypt (Case Rep Med 2011;2011:620480)
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
Additional references
Board review style question #1
Which statement regarding endemic goiter is false?
- Increases risk for follicular neoplasm
- Increases risk for papillary neoplasm
- May cause tracheal compression
- 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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Reference: Endemic goiter
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