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Related Experiment Videos

Delayed puberty in lambs chronically treated with oestradiol.

D L Foster, K D Ryan, R L Goodman

    Journal of Reproduction and Fertility
    |September 1, 1986
    PubMed
    Summary

    Low-dose estradiol treatment in female lambs delayed reproductive cycles and puberty onset. This suggests that sustained low luteinizing hormone (LH) secretion is crucial for ovarian development before sexual maturity.

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    Area of Science:

    • Reproductive Endocrinology
    • Animal Science
    • Developmental Biology

    Background:

    • Puberty onset in female mammals is regulated by complex hormonal interactions.
    • Luteinizing hormone (LH) plays a critical role in initiating reproductive cycles.
    • The impact of chronic low-level estradiol exposure on pubertal development in intact females is not fully understood.

    Purpose of the Study:

    • To investigate the effect of chronic low-dose estradiol administration on the initiation of reproductive cycles in intact female lambs.
    • To determine if estradiol treatment delays the onset of puberty and alters LH secretion patterns.
    • To explore the necessity of pre-pubertal LH secretion for ovarian function development.

    Main Methods:

    • Intact female lambs received chronic low-dose estradiol via Silastic implants from 20 weeks of age.

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  • Reproductive cycles were monitored until 45 weeks of age.
  • Serum LH levels were measured to assess tonic and pubertal secretion patterns.

    • Main Results:

    • Estradiol treatment significantly reduced the percentage of lambs initiating reproductive cycles (33% vs. 80% in controls).
    • The age at first estrus was delayed by approximately 3 weeks in treated lambs that did initiate cycles.
    • Estradiol could not suppress tonic LH secretion by 32 weeks of age, indicating a maturational decrease in sensitivity.

    Conclusions:

    • Chronic estradiol exposure delays pubertal onset and reproductive cyclicity in female lambs.
    • A maturational decrease in responsiveness to estradiol's inhibitory effect on LH secretion occurs before puberty.
    • Low tonic LH secretion, possibly in slow pulses, appears necessary for proper ovarian development and function prior to puberty.