Systemic and Intrafollicular Androgen Concentrations in Cycling Mares.
Authors: Satué Katiuska, Fazio Esterina, Cravana Cristina, Medica Pietro
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Systemic and Intrafollicular Androgen Concentrations in Cycling Mares Androgens are known to influence follicle development, yet their specific roles within the follicle itself remain incompletely understood in mares. Researchers analysed follicular fluid and blood samples from 60 ovaries (collected post-slaughter from 30 clinically healthy mares) to measure three key androgens—testosterone (T), androstenedione (A4), and dehydroepiandrosterone (DHEA)—across three follicle size categories (small: 20–30 mm; medium: 31–40 mm; large: ≥41 mm). Intrafollicular concentrations of all three androgens substantially exceeded systemic levels, with A4 emerging as the predominant intrafollicular androgen; notably, T and A4 increased progressively with follicle diameter whilst DHEA showed an inverse relationship, suggesting a biotransformation pathway from DHEA through A4 to T within the developing follicle. Strong positive correlations between systemic and intrafollicular T and A4 indicate that blood hormone measurements may reflect intrafollicular activity, potentially offering practitioners a non-invasive window into follicular steroidogenesis. These findings advance understanding of the hormonal microenvironment supporting oestradiol production and follicle maturation, with implications for optimising breeding programmes, managing ovulatory dysfunction, and refining hormone-based fertility interventions in mares.
Read the full abstract on PubMed
Practical Takeaways
- •Understanding the androgenic microenvironment in developing follicles provides insight into normal reproductive physiology in mares, which may help inform management of breeding programs and reproductive disorders
- •The shift in androgen metabolism from DHEA in small follicles to testosterone and androstenedione in larger follicles reflects the physiological preparation for ovulation and oestradiol production
- •Systemic androgen measurements may serve as a non-invasive indicator of intrafollicular androgen status during follicular development cycles
Key Findings
- •Intrafollicular concentrations of testosterone, androstenedione, and DHEA were significantly higher than systemic concentrations in cycling mares
- •Androstenedione was the predominant androgen in follicular fluid, with testosterone and androstenedione increasing with follicle size (medium and large follicles > small follicles)
- •DHEA showed negative correlation with follicular diameter and was significantly higher in small follicles than medium and large follicles
- •Strong positive correlations existed between systemic and intrafollicular testosterone and androstenedione, suggesting biotransformation of DHEA to androstenedione to testosterone within developing follicles