Endocrine System

Parathyroid Gland

Narrative

The paired parathyroid glands are typically located on the anterolateral edge of the thyroid glands. In the rat they are 1-2 mm in length and considerably larger in females than in males. Accessory parathyroid tissue is sometimes located adjacent to the thymus. Parathyroids are lightly encapsulated and consist of highly folded branching cords and nests of polygonal cells separated by a delicate fibroreticular stroma. The principal cell type in the rat is the chief cell with a spherical to oval nucleus. Tinctorial properties of the cytoplasm vary, and the presence of clear or dark cells reflects different functional status of the chief cells. Chief cells in the mouse parathyroid may be clear or dark, with an increase in clear cells in older mice. Cytoplasmic volume or nuclear density of the chief cells (on a glandular level) is a relative indicator of parathyroid hormone synthesis and secretion. Glands with larger chief cells due to greater cytoplasmic volume are typically more active. Changes in cell density and morphology may be subtle, so side-by-side comparison of study control parathyroid glands with those of treated rodents is recommended to best assess these changes.

Image of normal in the parathyroid gland from a male F344/N rat in a chronic study

Figure 1. Parathyroid Gland - Normal in a male F344/N rat from a chronic study. The normal parathyroid is lightly encapsulated and located on the edge of the thyroid.

Image of normal parathyroid gland from a male F344/N rat in a chronic study

Figure 2. Parathyroid gland - Normal in a male F344/N rat from a chronic study. This higher magnification of Figure 1 shows the nests and chords of polygonal cells separated by a delicate fibroreticular stroma in a male F344/N rat from a chronic study.

Image of normal parathyroid gland from a male B6C3F1 mouse in a chronic study

Figure 3. Parathyroid gland - Normal in a male B6C3F1 mouse from a chronic study. Normal parathyroid located at the edge of the thyroid.

Image of normal parathyroid gland from a male B6C3F1 mouse in a chronic study

Figure 4. Parathyroid gland - Normal in a male B6C3F1 mouse from a chronic study. This higher magnification of Figure 3 shows the nests and cords of polygonal cells separated by a delicate fibroreticular stroma.

Authors and Reviewers

Authors

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

Georgette D. Hill, D.V.M., Ph.D.
Toxicologic Pathologist/Assistant Pathology Program Manager
Comparative Molecular Pathology Division
Integrated Laboratory Systems, 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

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