Changes in estrone and estradiol levels during follicle development: a retrospective large-scale study

Area of Science:

• Reproductive Endocrinology
• Clinical Chemistry
• In Vitro Fertilization

Background:

• The ST AIA-PACK iE2 reagent offers improved specificity for estradiol (E2) measurement compared to the original ST AIA-PACK E2 reagent due to lower estrone (E1) cross-reactivity.
• Understanding E1 and E2 level dynamics during follicle development is crucial for accurate assessment in fertility treatments.

Purpose of the Study:

• To analyze changes in estrone (E1) and estradiol (E2) levels during follicle development using two different measurement reagents.
• To compare E2 measurements obtained with the original ST AIA-PACK E2 reagent and the improved ST AIA-PACK iE2 reagent.

Main Methods:

• Analysis of 14,371 serum hormone measurements from 4,412 patients undergoing in vitro fertilization (IVF) between June 2011 and May 2014.
• Patients were stratified by age (<38, 38-40, >40 years) and largest follicle diameter (11-20 mm).
• Serum E2 levels were measured using either ST AIA-PACK E2 or ST AIA-PACK iE2 reagent; E1/E2 ratios were compared in 26 samples.

Main Results:

• ST AIA-PACK iE2 reagent showed significantly lower E2 concentrations than ST AIA-PACK E2 reagent in specific follicle diameter ranges across age groups.
• The difference in E2 measurements decreased as follicle diameter increased, particularly in older patients.
• Serum E1/E2 ratios were higher in the early follicular phase (3.4 ± 1.1) compared to the ovulatory phase (0.7 ± 0.1).

Conclusions:

• The observed differences in E2 measurements between reagents are influenced by follicle development stage and patient age.
• Higher E1 levels are suggested in the early follicular phase and in younger patients compared to the ovulatory phase and older patients.
• These findings highlight the importance of reagent specificity in hormone level interpretation during fertility assessments.