Increase In Luteinizing Hormone Levels Research Articles

Plasma levels of luteinizing hormone in gonadectomized Japanese quail exposed to short or to long daylengths.

Plasma levels of luteinizing hormone (LH) were measured by radioimmunoassay in gonadectomized male and female Japanese quail, exposed either to 8 h light: 16 h darkness per day (8L:16D; short days) or to 20L:4D (long days). In both sexes, exposure to long days increased LH levels and in the gonadectomized quail LH continued to rise over several weeks. Eventually the castrated quail had levels about five times higher than the control birds and the ovariectomized quail had levels about 14 times higher than their controls. Quail kept on short days had low LH levels while birds kept on long days and returned to short days resumed low levels after a delay of some days. Since very high levels of LH occurred in gonadectomized quail only when they were on long days, we conclude that the photoperiodic regulation of LH secretion does not operate solely by adjusting sensitivity to gonadal feedback, but works in a more direct manner. Ovariectomized females whether on long days (high LH) or short days (low LH) grew masculine plumage and castrated males retained male plumage. This confirms that the ovary is responsible for sexual dimorphism of plumage and shows that the action of the ovary is not mediated by LH (through feedback). The remaining rudimentary (right) gonad in ovariectomized females did not undergo visible hypertrophy and did not secrete enough hormone to stimulate the cloacal gland or oviduct.

The effect of mating on the afternoon of proestrus on serum LH (and FSH) and ovulation in the rat.

Possible relationships between coitus and serum gonadotrophin levels and ovulation in the rat were investigated. Female rats were mated betw een 1700 and 1730 or between 1800 and 1830 hours. 1.3 ml of blood was withdrawn by cardiac puncture 30 minutes postcoitus for luteinizing hormone (LH) analysis. After autopsy on the morning of estrus, counts were made of tubal ova, and LH and follicle-stimulating hormone (FSH) were measured in terminal blood from all animals. Those mated at 1700-1730 with no cardiac puncture showed significantly more ova than those with cardiac puncture (p less than .05) and those which were neither mated nor received cardiac puncture (p les than .05). No differences were found between those mated at 1800-1830 hours because of the large variance in each group. Coitus during the time of normal mating did not increase LH levels 30 minutes postmating or terminal LH and FSH levels. Terminal LH levels were significantly increased in the no cardiac puncture-no mate animals (p less than .05) in comparison with the cardiac puncture-no mate animals.

Studies on the luteinizing hormone- and follicle-stimulating hormone-releasing mechanism in the testicular feminization syndrome: Hypothalamic-pituitary responsiveness to clomiphene, luteinizing hormone-releasing hormone, gonadectomy, and sexual steroids

The follicle-stimulating hormone (FSH) and luteinizing hormone (LH) secretory response to various stimuli was studied in 4 adult siblings with the complete form of testicular feminization. Before gonadectomy, the 4 patients had elevated serum levels of both LH and FSH. Clomiphene administered for 7 days did not change the serum levels of gonadotropins. LH-releasing hormone (LH-RH) administration resulted in FSH release above the range observed in normal adult men and women; however, the maximum LH increase was not different from that of normal adults. Gonadectomy elicited a further and significant elevation of both FSH and LH levels. After castration, serum levels of LH and FSH exhibited a further increase following LH-RH administration comparable quantitatively to that before castration. The FSH secretory response to LH-RH was greater than that of LH. The administration of progesterone alone to the 4 patients already castrated did not result in any major change in the serum levels of FSH and LH. Estrogen administration decreased the high levels of gonadotropins. The relative decrease for FSH was greater than for LH, and, when progesterone was given following 4 weeks of estrogen treatment, an increase in the serum levels of LH was found; there was also a small increase in FSH concentration. It is concluded from this study that in testicular feminization: (1) There is a partial gonadal feedback control of both FSH and LH secretion; (2) hypothalamic receptors are not sensitive to the stimulatory effect of clomiphene; (3) there is an unusually large amount of FSH released by the pituitary after intravenous LH-RH; (4) FSH and LH secretion are readily suppressed by estrogen administration; (5) there is a positive feedback effect of progesterone upon serum gonadotropins in estrogen-primed castrated patients with testicular feminization.

Involvement of Catecholamines in Feedback Mechanisms

The stimulatory effects of estrogen and progesterone on luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release were studied in rats to investigate the possible participation of catecholamines (CA) in mediating steroid-feedback effects. Progesterone or estrogen administration caused a sharp increase in levels of LH and FSH in estradiol-primed spayed females. Phenoxybenzamine block of alpha-adrenergic receptors completely eliminated the gonadotropin peaks. Haloperidol had a similar effect. The administration of alpha-methyl-p-tyrosine (alpha-MPT), which produces a marked decline in noradrenaline (NA) and dopamine (DA), also blocked the progesterone-induced increase in FSH and LH. Diethyldithiocarbamate (DD C) and 1-phenyl-3-(2-thiazolyl)-2-thiourea (u-14, 624) were each effective in blocking the progesterone- or estrogen-induced increase in gonadotropin release. Treatment with dihydroxyphenylaline (DOPA) or dihydroxyphenylserine (DOPS) restored DA and/or NA levels. However, when conversion of DA to NA was blocked by DDC, the admininstration of DOPA was ineffective in restoring levels of LH and FSH in alpha-MPT-treated rats, although DOPS was effective. The results indicate that NA has a predominant role in transmitting the stimulatory effects of estrogen and progesterone on the release of LH and FSH.

Gonadotropin levels in puberty. I. Serum luteinizing hormone.

ABSTRACT Serum luteinizing hormone (LH) concentrations have been determined by a specific radioimmunoassay in 175 boys and girls from 8 through 15 yr of age. The data show that serum LH was detectable at 8 yr for both boys and girls and that there was a progressive rise in serum LH concentrations as sexual maturity was reached. However, there appears to be a quantitative and qualitative difference in the LH increments between boys and girls: consistently higher serum LH concentrations were observed in girls than in boys. There was a 9-fold increase in the mean serum LH concentration in pubescent girls and only a 3-fold increase in pubescent boys. By age 14, the mean serum LH concentration in girls was reaching the adult female levels, but there was only 30% of adult male levels in boys. In addition, menarche was associated with a significant rise in the mean seimm LH concentration. These findings indicate that the correlation between changes accompanied with puberty and increased LH levels in girls is mor...