Microscopic and Histochemical Assessment of Structural Changes in the Human Thyroid Gland across Different Age Groups

Abstract

Background: Aging is associated with progressive structural and functional changes in the thyroid gland.

Objective: To assess microscopic and histochemical structural changes in the human thyroid gland across different age groups.

Methods: This comparative cross-sectional histomorphological study was conducted at Anatomy department in collaboration with Medicine  department of DG Khan Medical College, DG Khan from January 2026 to June 2026, included 90 human thyroid specimens divided equally into three age groups: 18–35 years, 36–55 years, and 56–75 years. Routine hematoxylin and eosin staining was performed to assess general thyroid architecture, follicular size and shape, epithelial cell height, colloid content, stromal changes, vascularity, and the presence of age-related structural alterations.

Results: Mean follicular diameter increased significantly from 112.36±18.42 µm in the youngest group to 128.71±21.55 µm and 151.84±25.63 µm in the middle and older groups, respectively (p<0.001). Follicular epithelial height decreased from 8.42±1.31 µm to 7.36±1.24 µm and 6.18±1.17 µm (p<0.001). Colloid area increased from 54.63±7.85% to 61.72±8.41% and 69.58±9.12%, while stromal connective tissue increased from 11.48±3.62% to 16.37±4.18% and 23.76±5.43% (p<0.001). Irregular follicles, epithelial flattening, stromal fibrosis, vascular wall thickening, and lymphocytic infiltration were more frequent with advancing age.

Conclusion: Advancing age was associated with progressive follicular enlargement, epithelial flattening, colloid accumulation, reduced vascularity, increased fibrosis, and greater collagen deposition in the human thyroid gland.