= Luteinizing hormone
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= LH
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<Luteinizing hormone> (<LH>) is a <glycoprotein> <gonadotropin> released by <gonadotrophs> in the <anterior pituitary> under control of <gonadotropin-releasing hormone>. It participates in <ovulation> and formation of the <corpus luteum>, and promotes <testosterone> production in the <testis>. The <hormone>'s output is regulated within interacting pituitary and gonadal feedback pathways.<Anatomy and Physiology 2e by J. Gordon Betts and others>[Section 17.3: Luteinizing Hormone and the pituitary hormone summary]{ref}
The shape of a <LH> surge can be investigated by measuring several signals through time. In 1983, <J. D. Hoff> and colleagues studied five women with hormone measurements every two hours for five consecutive days around midcycle. They compared <estradiol>, <progesterone> and gonadotropin trajectories, finding an abrupt onset of the <LH> and <follicle-stimulating hormone> surges in temporal association with the estradiol peak.<Hormonal dynamics at midcycle: a reevaluation by J. D. Hoff and others>[Abstract: sampling schedule, surge onset and the associated ovarian hormone changes]{ref}
The report included a doubling of <LH> within a two-hour interval at surge onset. Such a change illustrates why sampling frequency matters: coarse measurements can blur an abrupt transition or shift the apparent ordering of events. The study describes a measured cohort pattern; it does not turn one isolated <hormone> measurement into a complete account of the cycle.
The relation to <GnRH> can also be probed by paired portal and peripheral <blood plasma> measurements. The <hypophyseal portal system> makes those two locations physiologically different: one carries the hypothalamic input, while the other records the pituitary's released output.
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