This describes the normal, cyclical, and often pronounced variations in the concentration of sex steroids, such as estrogen, progesterone, and testosterone, and their pituitary regulators, LH and FSH, particularly evident during the menstrual cycle and the perimenopausal transition. While fluctuation is a natural state, excessive or unpredictable variability can lead to symptoms like mood disturbance, irregular cycles, or loss of bone density. Clinical management often focuses on mitigating extreme fluctuations to restore stability and enhance quality of life.
Origin
The term is central to reproductive endocrinology, describing the dynamic nature of the hypothalamic-pituitary-gonadal (HPG) axis in fertile individuals and during reproductive aging. “Reproductive hormone” specifies the class of signaling molecules, and “fluctuation” captures the inherent variability of their concentration over short and long time scales.
Mechanism
The mechanism is controlled by the pulsatile release of Gonadotropin-Releasing Hormone (GnRH) from the hypothalamus, which drives the cyclical release of LH and FSH from the pituitary. These gonadotropins then stimulate the gonads to produce sex steroids in a predictable, feedback-regulated pattern. During reproductive aging, the ovaries become less responsive, leading to erratic feedback signals and subsequent erratic, high-amplitude fluctuations in pituitary and gonadal hormones, marking the perimenopausal state.
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