L‐hydroxytryptophan amplifies pulsatile secretion of LH in the follicular phase of normal women

Abstract

Pulsatile administration of L-5-hydroxytryptophan increases LH pulse amplitude in the follicular phase of normal women. In the absence of GnRH, L-5-hydroxytryptophan does not stimulate pituitary LH secretion.

Chickpea domestication in the Neolithic Levant through the nutritional perspective

“…Thus, higher ovulation rates may be an outcome of increasing dietary tryptophan. Plasma tryptophan levels may decrease following lactation in women, leading to decreased ovulation rates (Downing et al, 1997;Lado-Abeal et al, 1997), and increased demand for tryptophan. Serotonin is also implicated in cognitive ability and impulsivity (Clarke et al, 2004), while tryptophan depletion in humans has little effect on the performance of tasks activating the dorsolateral region of the prefrontal cortex, such as spatial working memory or planning (Park et al, 1994).…”

L‐5‐hydroxytryptophan does not stimulate LH secretion directly from the pituitary in patients with gonadotrophin releasing hormone deficiency

“…Unlike many other neurotransmitters, including catecholamines (Veldhuis et al ., 1983; Kaufman & Vermeulen, 1989), opioids (Yen et al ., 1985) and GABA (Lado Abeal et al ., 1996), serotonin has been the subject of relatively little research (Urban & Veldhuis, 1990; Pijl et al ., 1993; Ulrich et al ., 1994) in connection with the regulation of LH secretion in humans, although its involvement in LH regulation in rats is supported by considerable histological (Parent et al ., 1981; Steinbusch, 1984; Kiss & Halász, 1985) and physiological (Vitale & Chiocchio, 1993) evidence. However, we recently found (Lado‐Abeal et al ., 1997) that pulsatile administration of L ‐5‐hydroxytryptophan (5‐HTP, the immediate precursor of serotonin) amplifies LH secretion in women in the follicular phase so long as they have an active GnRH pulse generator. Neither the frequency nor the duration of LH pulses are affected, and the effect on pulse amplitude is not due to 5‐HTP directly inducing LH secretion by the pituitary.…”

“…At 1300 and 1600 h each subject was given 75 mg oral doses of the aromatic‐ L ‐amino‐acid decarboxylase inhibitor carbidopa (DuPont Pharma S.A., Spain). At 1600, 1700 and 1800 h, intravenous 5‐HTP (Farma Lepori S.A., Spain) was administered at doses calculated using a pharmacokinetic model described previously (Lado‐Abeal et al ., 1997), so as to maintain the serum 5‐HTP concentration below the toxic threshold of 6 μmol/l (all doses were between 8 and 20 mg).…”

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“…Most experiments investigating the effects of 5-HT on reproductive function have been performed in rats, where it seems that 5-HT can be either stimulatory or inhibitory to LH release depending on the circulating steroid milieu (17). There is also evidence implicating 5-HT in the regulation of sexual behavior as well as gonadotropin secretion in humans (39,40). A direct effect of 5-HT on GnRH secretion is suggested by the observations that serotonergic fibers terminate in the proximity of GnRH perikarya/fibers (41).…”