From menarche to regular menstruation: endocrinological background.

Area of Science:

• Reproductive Endocrinology
• Neuroendocrinology
• Gynecology

Background:

• Hormone secretion patterns change significantly from childhood to adulthood.
• Gonadotropin-releasing hormone (GnRH) secretion is suppressed before puberty and increases at its onset.
• The hypothalamic gonadostat and feedback mechanisms play crucial roles in pubertal development and reproductive cyclicity.

Purpose of the Study:

• To describe the hormonal changes during the transition from childhood to adulthood.
• To elucidate the roles of various hormones in regulating the hypothalamic-pituitary-ovarian axis.
• To explain the establishment of normal menstrual cyclicity.

Main Methods:

• Review of existing literature on hormonal changes during puberty and the menstrual cycle.
• Analysis of the regulatory roles of key hormones including GnRH, FSH, LH, estradiol, progesterone, and inhibins.
• Examination of feedback mechanisms (negative and positive) in the hypothalamic-pituitary system.

Main Results:

• Puberty involves the derepression of the hypothalamic gonadostat, increased GnRH pulse amplitude, and rising FSH and LH levels.
• Estradiol and progesterone regulate FSH and LH secretion, while inhibins control FSH secretion.
• Gonadotropin surge attenuating factor (GnSAF) modulates the midcycle LH surge by counteracting estradiol's sensitizing effect.

Conclusions:

• The transition to adulthood involves complex hormonal regulation of the reproductive system.
• Both steroidal and nonsteroidal ovarian hormones are critical for maintaining normal menstrual cycles.
• Understanding these hormonal dynamics is essential for reproductive health.