Scanning electron microscopy of the normal human thyroid

Area of Science:

• Endocrinology
• Cell Biology
• Microscopy

Background:

• The thyroid gland's function is regulated by complex cellular mechanisms.
• Understanding follicular cell morphology provides insights into thyroid activity.

Purpose of the Study:

• To investigate the relationship between apical cell surface morphology and microvilli density in normal human thyroid tissue.
• To explore the potential functional significance of observed morphological variations, including the presence of cilia.

Main Methods:

• Scanning electron microscopy (SEM) was used to examine normal thyroid specimens from 20 euthyroid patients.
• Concurrent transmission electron microscopy (TEM) was employed to correlate apical membrane morphology with cellular activity.
• Quantitative analysis of apical cell surface diameter and microvilli density was performed.

Main Results:

• A significant negative correlation was observed between apical cell surface diameter and microvilli density.
• Larger follicles were associated with smooth-surfaced cells, while smaller follicles had cells with dense microvilli.
• One to five cilia were consistently found on normal follicular cells, with no correlation to microvilli density or surface diameter.

Conclusions:

• Thyroid follicular cell morphology, particularly microvilli density, is inversely related to apical surface area, suggesting an intrafollicular functional cycle.
• The presence of cilia on follicular cells may indicate a functional role, potentially in stirring colloid.
• Morphological variations within and between follicles highlight the dynamic nature of thyroid cell activity.