Anti-Müllerian hormone and ovarian aging in mares

in Journal of Endocrinology
Correspondence should be addressed to R C Uliani or A J Conley: or
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Anti-Müllerian hormone (AMH) is used as a marker of follicle population numbers and potential fertility in several species including horses but limited data exist across the lifespan. No one has decreased ovarian reserve experimentally to investigate whether a corresponding, quantitative decrease in AMH results. Concentrations of AMH across the lifespan were compiled from 1101 equine females sampled from birth to >33 years of age. Young and old mares (averaging 6 and 19 years) were hemi-ovariectomized and circulating AMH was assessed before and daily thereafter for 15 days. The remaining ovary was removed later and blood was drawn again before and after this second surgery for AMH determination. Polynomial regression analysis and analysis of mares grouped by 5-year intervals of age demonstrated AMH concentrations to be higher in mares aged 5–10 and 10–15 years than 0–5 years of age and lower in mares after 20 years of age. There was high variability in AMH concentrations among neonatal fillies, some of which had concentrations typical of males. Hemi-ovariectomy was followed by a decrease of AMH, almost exactly halving concentrations in intact mares. Concentrations of AMH had returned to intact levels in old mares before complete ovariectomy, as if exhibiting ovarian compensatory hypertrophy, but recovery of AMH was not evident in young mares. AMH may reflect ovarian senescence in mares after 20 years of age but is too variable to do so in the first two decades of life. The ovarian endocrine response to hemi-ovariectomy in mares appears to change with age.

Downloadable materials

  • Supplementary Figure 1. Parallelism of optical densities (arbitrary units) from serial dilutions of a mare sample pool (diamonds) assayed and plotted alongside the AMH assay standard curve (ng/ml, squares).
  • Supplementary Figure 2. Optical densities generated by recombinant human anti-Mullerian hormone (rhAMH, ng/ml) that was added to assay buffer (dots, solid line) or equine (gelding) serum (triangle, dashed line) within the range of kit calibrators (0-15.6 ng/ml).
  • Supplementary Figure 3. Recovered recombinant human AMH (Measured AMH, ng/ml) after recombinant human AMH (rhAMH, ng/ml) was added to equine (gelding) serum and assayed, showing the linear regression relationship (y=0.52x, R2=0.99) across a working range of concentrations.
  • Supplementary Figure 4. Correlation between concentrations of AMH in a sub-set of samples (n=43) re-assayed after re-freezing and storage.
  • AFC by US - Before first surgery


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    Concentrations of anti-Müllerian hormone (AMH, ng/mL) in populations of mares (N = 1101) sampled at various ages ranging from birth to >33 years of age. Changes in AMH concentrations with age were analyzed by linear regression analysis performed based on mare ages (0–10, 11–20 and >20 years of age). Linear regression was not significant for ages 0–10 (P > 0.41) or 11–20 (P > 0.48) years of age, but declined significantly with age in mares >20 years of age (P < 0.001).

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    Non-parametric analysis of concentrations of anti-Müllerian hormone (AMH, ng/mL) in populations of mares, grouped by 5-year age ranges (N = 1058; <5 years, n = 399; 5–10 years, n = 272; 10–15 years, n = 193; 15–20 years, n = 110; 20–25 years, n = 64; >25 years, n = 20). Data from day-old fillies (n = 43) were omitted from this analysis. Shown are the median concentrations, ranges and 50% confidence intervals. AMH concentrations in intervals marked by different superscript differ, P < 0.05.

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    Concentrations of anti-Müllerian hormone (AMH, ng/mL) in young (6.0 ± 0.8 years, dashed line, n = 6) and old mares (18.7 ± 0.5, solid line, n = 6) in jugular blood drawn before (day 0) and daily after hemi-ovariectomy. Concentrations of AMH decreased significantly from day 0 (pre-hemi-ovariectomy) to day 15 (P < 0.001) after surgery, but there was no main effect of age or age * time interaction, and there was no difference in AMH between young and old mares on day 0 (P > 0.5).

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    Concentrations of anti-Müllerian hormone (AMH, ng/mL) in young (6.0 ± 0.8 years, dashed line, n = 6) and old mares (18.7 ± 0.5, dotted line, n = 6) in jugular blood drawn before (PRE-HEMI) and 15 days after (POST-HEMI) hemi-ovariectomy, and before (PRE-OVX) and after (POST-OVX) complete ovariectomy when mares were anestrous. †Indicates concentrations of AMH were significantly lower (P < 0.01) than before hemi-ovariectomy. AMH concentrations were not different between young and old mares before ovariectomy (PRE-OVX) but the age * time interaction was significant (P < 0.02). Lines are broken to signify that intervals between post-HEMI and pre-OVX varied (111 ± 24 days), but data were true longitudinal samples and analyzed as repeated measures accordingly. Means are represented by solid symbols, and individual values from all mares are depicted as open symbols.


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