Thecal Thinning in Ovarian Follicular Atresia: Histopathology and Significance
Thecal thinning (narrowing of the theca cell layer) is a hallmark of follicular atresia—the degenerative resorption of ovarian follicles that fail to ovulate (>99% of follicles).
Process
- Granulosa cell apoptosis: Initiated by loss of FSH survival signaling, oxidative stress, Fas/FasL pathway.
- Basement membrane breakdown: MMPs degrade collagen IV → loss of structural integrity.
- Theca cell regression: Theca externa (connective tissue) and theca interna (steroidogenic) cells undergo atrophy, reduced vascularity, and apoptosis. Androgen production ceases.
- Macrophage infiltration: Phagocytose cellular debris; remodel extracellular matrix.
- Final resorption: Follicle collapses; hyalinized scar (corpus fibrosum) may remain.
Significance
- Theca thinning reflects loss of androgen substrate for estrogen synthesis (two-cell, two-gonadotropin model).
- Excessive atresia → diminished ovarian reserve.
- Histologic staging of atresia aids ovarian aging research.
Understanding atresia informs fertility preservation and ovarian aging therapies.
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