Episodic secretory patterns of immunoreactive luteinizing hormone-releasing hormone (IR-LH-RH) in the systemic circulation of normal women throughout the menstrual cycle

Abstract

Using established radioimmunoassays for measuring plasma luteinizing hormone-releasing hormone (LH-RH) and serum gonadotropins, we studied the secretory dynamics of these hormones in eight normal ovulatory women during different phases of their menstrual cycle. All of the women demonstrated evidence of pulsatile immunoreactive LH-RH (IR-LH-RH) release throughout the cycle, with IR-LH-RH concentrations fluctuating between 0.5 and 35 pg/ml in the systemic circulation. Analysis of IR-LH-RH episodic secretions revealed a significant increase of both mean IR-LH-RH concentrations (P less than 0.001) and pulse frequency (P less than 0.05) during the periovulatory period. Furthermore, plasma IR-LH-RH titers in five normal women studied during the morning and night at mid-menstrual cycle fluctuated markedly, with slightly greater episodic discharges observed during the night than in the morning (P less than 0.05) and no significant change in pulse frequency.