Endocrine System

Thyroid Gland, Follicular Cell - Hypertrophy

Narrative
Comment:
In follicular cell hypertrophy, thyroid follicles may be lined by cuboidal to columnar epithelium with central follicles tightly packed and smaller than normal (Figure 1 and Figure 2). Focal hyperplasia of follicular epithelium may sometimes accompany follicular hypertrophy (Figure 1, arrows). Bilateral hypertrophy is expected as a systemic response to increased pituitary secretion of thyroid-stimulating hormone. Hypertrophic follicular epithelium may contain pale eosinophilic cytoplasm and small clear vacuoles (Figure 3). In more chronic follicular epithelial hypertrophy, all follicles may be smaller than normal, with secretory depletion or abnormal secretion and exfoliated epithelium (Figure 4). The presence of thyroid follicular cell hypertrophy may be secondary to hepatocellular microsomal enzyme induction, and hepatocellular hypertrophy is often seen concomitantly in rats with thyroid gland follicular cell hypertrophy.
Recommendations:
Thyroid follicular cell hypertrophy should be diagnosed and graded when present. The pathology narrative can describe the nature of the hypertrophic follicular epithelium and whether bilateral, accompanied by follicular hyperplasia, or associated with alterations in colloid.
References:

Capen CC, Martin SL. 1989. The effects of xenobiotics on the structure and function of thyroid follicular and C-cells. Toxicol Pathol 17:266-293.

Abstract: http://www.ncbi.nlm.nih.gov/pubmed/2675279

Capen CC, DeLellis RA, Yarrington JT. 2002. Endocrine system. In: Handbook of Toxicologic Pathology, Vol 2 (Haschek WM, Rousseaux CG, Wallig MA, eds). Academic Press, New York, 681–783.

Abstract: http://www.sciencedirect.com/science/book/9780123302151

Collins WT, Capen CC, Kasza L, Carter C, Dailey RE. 1977. Effect of polychlorinated biphenyl (PCB) on the thyroid gland of rats. Ultrastructural and biochemical investigations. Am J Pathol 89:119-136.

Abstract: http://www.ncbi.nlm.nih.gov/pubmed/199066

Greaves P. 2007. Histopathology of Preclinical Toxicity Studies: Interpretation and Relevance in Drug Safety Evaluation, 3rd ed. Academic Press, Amsterdam, 819-839.

Abstract: http://www.sciencedirect.com/science/book/9780444527714

Hardisty JF, Boorman GA. 1990. Thyroid gland. In: Pathology of the Fischer Rat: Reference and Atlas (Boorman GA, Eustis SL, Elwell MR, Montgomery CA, MacKenzie WF, eds). Academic Press, San Diego, 519–536.

Abstract: http://www.ncbi.nlm.nih.gov/nlmcatalog/9002563

Hood A, Hashmi R, Klaassen CD. 1999. Effects of microsomal enzyme inducers on thyroid-follicular cell proliferation, hyperplasia, and hypertrophy. Toxicol Appl Pharmacol 160:163-170.

Abstract: http://www.ncbi.nlm.nih.gov/pubmed/10527915

Stevens JT. 1985. Effect of chemicals on the thyroid gland. In: Endocrine Toxicology (Thomas JA, Korach KS, McLachlan JA, eds). Raven Press, New York, 135–147.

Abstract: http://informahealthcare.com/doi/book/10.3109/9781420093100
  • Image of follicular cell hypertrophy in the thyroid gland from a male F344/N rat in a subchronic study

    Thyroid Gland, Follicular Cell - Hypertrophy in a male F344/N rat from a subchronic study. Focal hyperplasia is present in two adjacent follicles (arrows).

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Thyroid Gland, Follicular Cell - Hypertrophy in a male F344/N rat from a subchronic study. Focal hyperplasia is present in two adjacent follicles (arrows).
Thyroid Gland, Follicular Cell - Hypertrophy in a male F344/N rat from a subchronic study. Focal hyperplasia is present in two adjacent follicles (arrows).
Thyroid Gland, Follicular Cell - Hypertrophy in a male F344/N rat from a subchronic study. Higher magnification of Figure 1 shows the epithelium lining the follicles is cuboidal to columnar.
Thyroid Gland, Follicular Cell - Hypertrophy in a male F344/N rat from a subchronic study. Higher magnification of Figure 1 shows the epithelium lining the follicles is cuboidal to columnar.
Thyroid Gland, Follicular Cell - Hypertrophy in a male F344/N rat from a subchronic study. The cuboidal to columnar lining epithelium contains small, clear, cytoplasmic vacuoles.
Thyroid Gland, Follicular Cell - Hypertrophy in a male F344/N rat from a subchronic study. The cuboidal to columnar lining epithelium contains small, clear, cytoplasmic vacuoles.
Thyroid Gland, Follicular Cell - Hypertrophy in a female Sprague-Dawley rat from a chronic study. Follicles are smaller than normal, are lined by cuboidal epithelium, and contain amphophilic, flocculant-appearing material and exfoliated epithelial cells.
Thyroid Gland, Follicular Cell - Hypertrophy in a female Sprague-Dawley rat from a chronic study. Follicles are smaller than normal, are lined by cuboidal epithelium, and contain amphophilic, flocculant-appearing material and exfoliated epithelial cells.

Authors

Robert R. Maronpot, DVM, MS, MPH, DACVP, DABT, FIATP
Senior Pathologist
Experimental Pathology Laboratories, Inc.
Research Triangle Park, NC

Amy Brix, DVM, PhD, DACVP
Senior Pathologist
Experimental Pathology Laboratories, Inc.
Research Triangle Park, NC

Reviewers

Thomas J. Rosol, DVM, PhD, DACVP
Professor of Veterinary Biosciences
Senior Advisor, Life Sciences, Technology Commercialization and Knowledge Transfer
The Ohio State University
Columbus, OH

Susan A. Elmore, MS, DVM, DACVP, DABT, FIATP
Staff Scientist, NTP Pathologist
NTP Pathology Group
National Toxicology Program
National Institute of Environmental Health Sciences
Research Triangle Park, NC