LH secretion and testosterone concentrations are blunted after resistance exercise in men.

This study examined the hypothesis that exercise-induced changes in circulating testosterone would be centrally mediated via hypothalamic-pituitary release of luteinizing hormone (LH). We tested this hypothesis by examining overnight LH, total and free testosterone (TT and FT), and cortisol (C) concentrations in 10 young healthy men (21 +/- 1 yr) during two experimental sessions: a control and an acute heavy-resistance exercise bout (50 total sets consisting of squats, bench press, leg press, and latissimus dorsi pull-down). Exercise was performed from 1500 to 1700, and blood sampling began at 1700 and continued until 0600 the next morning. Blood was sampled every 10 min for LH and every hour for TT, FT, and C. Hormonal concentrations were determined via RIA, and the secretion characteristics of LH were analyzed with deconvolution analysis. When overnight postexercise concentrations were compared with control concentrations, no statistically significant (P < or = 0.05) differences were observed for LH half-life, LH pulse frequency, interpulse interval, pulse amplitude, or pulse mass. Significant differences were observed for LH production rate (13.6 +/- 4 and 17.9 +/- 5 IU. l distribution volume(-1) x day(-1) for exercise and control, respectively, a 24% reduction). For the ANOVA marginal main effect means due to condition, C was significantly elevated (5.9 +/- 0.7 vs. 4.0 +/- 0.4 microg/dl), while TT (464 +/- 23 vs. 529 +/- 32 ng/dl) and FT (15.6 +/- 0.7 vs. 18.3 +/- 0.9 pg/ml) were significantly decreased for the exercise condition. These data demonstrate that the decline in overnight testosterone concentrations after acute heavy-resistance exercise is accompanied by a blunted LH production rate and elevated C concentrations.     

The effect of FSH on LH induced testosterone secretion in the immature hypophysectomized male rat

The effect of gonadotropin pretreatment of hypophysectomized male rats on LH stimulated serum testosterone concentrations was studied. A 5 day pretreatment period began 2 days after hypophysectomy at 21 or 24 days of age. On the day following the pretreatment period the animals received an intraperitoneal injection of saline or LH 60 min before blood collection. Animals pretreated with NIH-FSH-B1, or with doses of LH approximating the amount present in the NIH-FSH, had increased testosterone concentrations after LH stimulation compared to similarly stimulated saline pretreated animals. Pretreatment with more highly purified FSH Ex 199C at a lower dose than the minimum effective dose of NIH-FSH was also effective. There was no synergistic or additive effect when FSH Ex 199C and LH pretreatments were combined. FSH Ex 199C is more potent and contains appreciably less LH contamination than NIH-FSH-B1. The results obtained using FSH Ex 199C indicate that FSH, independent of LH contamination, can increase testes response to LH stimulation.     

Glucose ingestion acutely lowers pulsatile LH and basal testosterone secretion in men

Chronic hyperglycemia inhibits the male gonadal axis. The present analyses test the hypothesis that acute glucose ingestion also suppresses LH and testosterone (T) secretion and blunts the LH-T dose-response function. The design comprised a prospectively randomized crossover comparison of LH and T secretion after glucose vs. water ingestion in a Clinical Translational Research Center. The participants were healthy men (n = 57) aged 19-78 yr with body mass index (BMI) of 20-39 kg/m(2). The main outcome measurements were deconvolution and LH-T dose-response analyses of 10-min data. LH-T responses were regressed on glucose, insulin, leptin, adiponectin, age, BMI, and CT-estimated abdominal visceral fat. During the first 120 min after glucose ingestion, for each unit decrease in LH concentrations, T concentrations decreased by 86 (27-144) ng/dl (r = 0.853, P < 0.001). Based upon deconvolution analysis, glucose compared with water ingestion reduced 1) basal (nonpulsatile; P < 0.001) and total (P < 0.001) T secretion without affecting pulsatile T output and 2) pulsatile (P = 0.043) but not basal LH secretion. By multivariate analysis, pulsatile LH secretion positively predicted basal T secretion after glucose ingestion (r = 0.374, P = 0.0042). In addition, the glucose-induced fall in pulsatile LH secretion was exacerbated by higher fasting insulin concentrations (P = 0.054) and attenuated by higher adiponectin levels (P = 0.0037). There were no detectable changes in the analytically estimated LH-T dose-response curves (P > 0.30). In conclusion, glucose ingestion suppresses pulsatile LH and basal T secretion acutely in healthy men. Suppression is influenced by age, glucose, adiponectin, and insulin concentrations.     

Alcohol decreases the alpha subunit, LH and testosterone secretion in response to LH-RH]

In our previous study we showed that alcohol disturbed the circadian rhythms of LH, testosterone and its conversion to DHT. To determine the effect of LH-RH on pituitary-gonadal function before and after alcohol, 11 male volunteers aged 24-29 years (mean 25.5) were investigated. Blood for hormonal estimations was withdrawn before and 20, 30, 60, and 120 min after LH-RH. In every case, the LH-RH test was performed twice: 6 hours after placebo and, a week later, 6 hours after alcohol administered orally, in dose of 1.0 g/kg bw. The LH, FSH, alpha-subunit and testosterone concentrations were measured with radioimmunological methods. Results: It was shown that alcohol significantly inhibited LH (p < 0.05), alpha-subunit (p < 0.02) and testosterone (p < 0.001) response to LH-RH stimulation, but not that of FSH.     

The effect of testosterone on LH and testosterone responses to GnRH in bulls

Clinical and andrological-spermatological investigations in male beagles revealed the status of the gonads before and after fistulating the vas deferens.When semen samples were collected reqularly, no siqnificant differences could be observed in comparison to ejaculates before surgical intervention, as judged by spermatological parameters. Only an increased incidence of immature spermatic cells was found. Changes in the gonads and spermatozoa respectively were found in animals with irregular collection of spermatozoa via fistula which induced irrep-arable occlusion of the fistula and subsequent spermio-stasis.Insemination of beagle bitches with spermatozoa from fistulae led to fertilisation of 3 animals from the group of 4.     

Seasonal pattern of LH and testosterone secretion in adult male fallow deer, Dama dama

At monthly intervals during the year blood samples were collected every 20 min for 12 h from 4 entire and 2 prepubertally castrated adult fallow deer bucks. In the entire bucks there were seasonal changes in mean concentrations and pulse frequencies of plasma LH. Mean concentrations in late summer and autumn were 3-6 times higher than during other seasons. LH pulse frequency was low (0-1 pulses/12 h) during most of the year and increased only during the 2-month period (January and February) that marked the transition from the non-breeding season to the autumn rut. During this period there was a close temporal relationship between pulses of LH and testosterone. However, during the rutting period (March and April) episodic secretion of testosterone, manifest as surges in plasma concentrations of 4-6 h duration, was not associated with any detectable pulses in LH although mean plasma concentrations of LH remained elevated. During the rut, the surges of plasma testosterone occurred at similar times of the day. Plasma profiles in May indicated very low concentrations of LH and testosterone secretion in the immediate post-rut period. Castrated bucks exhibited highly seasonal patterns of LH secretion, with mean plasma LH concentrations and LH pulse frequency being lowest in November (early summer) and highest in February and March (late summer-early autumn). Mean concentrations and pulse frequency of LH in castrated bucks were higher than for entire bucks at all times of the year.     

Effects of ovariectomy and estradiol replacement on naloxone induced LH secretion in the female rabbit

The effects of an opioid antagonist, naloxone, on the secretion of gonadotrophins were investigated in the long term ovariectomized rabbit. In the intact and acutely ovariectomized rabbit (2 days p.o.) naloxone at 10 mg/kg induced an increase of 260-300% in LH secretion at 40 min post-injection. From days 33-66 post-surgery naloxone at 10 mg/kg caused significant elevations in LH release even when animals were treated with estradiol benzoate 24 h previously. By contrast, treatment with oestradiol benzoate 3 h before naloxone abolished the LH increase. An LH surge could be elicited in these rabbits with GnRH treatment. These studies indicated that long term ovariectomy in the female rabbit does not completely remove the opioid control of GnRH release and that the LH response to naloxone is influenced by circulating estradiol levels.     

Regulation of gonadotrophin secretion in rams from birth to sexual maturity. I. Plasma LH, FSH and testosterone levels.

Plasma LH, FSH and testosterone concentrations were measured by radioimmunoassays in male crossbred Merino/Corriedale sheep from birth to 45 weeks of age. FSH levels were 11 and 22 ng/ml at birth, increased to peak levels (mean value of 47 ng/ml) at 5 weeks and fluctuated between 25 and 35 ng/ml for the next 40 weeks. Similarly, LH (less than 0-5 ng/ml) and testosterone (less than 38 ng/100 ml) levels were low at birth and were significantly elevated by 5 weeks of age. LH values varied betwen 0-9 and 3-0 ng/ml for the next 30 weeks and then a secondary rise occurred reaching levels of 2-4 ng/ml by the 41st week after birth. Concentrations of LH subsequently fell to levels observed in adult rams. Testosterone levels rose gradually between the 5th and the 25th week, and then increased rapidly to values of 270-517 ng/100 ml by the 41st week after birth, a time coincident with the peak LH levels. Histological examination of testicular biopsies demonstrated that Sertoli cell maturation occurred 17-21 weeks after birth and was followed by activation of spermatogenesis leading to the presence of spermatozoa in the seminiferous epithelium by 39-42 weeks of age.     

Effects of nutritional supplements on testicular size and the secretion of LH and testosterone in Merino and Booroola rams

Six Booroola and six Merino rams were fed either a diet which maintained constant live weight or the same diet plus a supplement of high protein lupin grain for 15 weeks, and changes in live weight and testicular volume were measured. Serial blood samples taken for 24 h before the start and 9 weeks after the treatment began were assayed for plasma LH and testosterone and the resulting profiles were analysed for pulses of both hormones. Five weeks later, the animals were given two intravenous injections of 1 μg gonadotrophin-releasing hormone (GnRH) 1 h apart in order to measure pituitary gland responsiveness. A further week later the animals were injected intravenously with 500 μg human chorionic gonadotrophin (hCG) and the levels of testosterone were measured in samples taken after 1.5 h to estimate the testicular responsiveness.The nutritional supplement stimulated testicular growth in both genotypes, so that at the end of the treatment period the testes had increased significantly (P<0.01) in volume by 66% in the Merinos and by 63% in the Booroolas. The live weights also increased, but by relatively less (34% and 43% for supplemented Merinos and Booroolas). The rates of increase in both testicular size and live weight were similar for the two breeds. There were no significant effects of diet on the tonic secretion of LH or testosterone, or on responsiveness to GnRH or hCG.The intervals between LH pulses were significantly shorter (P<0.05) in Booroola rams than in Merino rams both before and after treatment (5.8 h vs. 11.6 h before treatment). The breed differences in LH secretion were mimicked by the testosterone profiles. In the Booroolas, five of the twelve LH profiles contained groups consisting of two to four individually identifiable pulses, each of which elicited a separate pulse of testosterone. A pulse group was observed in only one profile from the Merinos (P=0.06). There were no significant differences between the genotypes in any other parameter of LH or testosterone secretion, or in their responsiveness to GnRH or hCG.It was concluded that (i) nutritional supplements will stimulate testicular growth in both Merino rams and Booroola rams; (ii) the increase in testicular size does not appear to involve an increase in the responsiveness of the testis to LH; and (iii) there are both qualitative and quantitative differences between the genotypes in the patterns of secretion of LH and testosterone which may be associated with the differences in their fecundity.     

The effect of LH-RH administration on LH release in the female rabbit.

Intracarotid infusion of LH-RH to female rabbits stimulated a significant increase in plasma LH concentration in the jugular vein. This response varied with the reproductive state of the animal, with a greater release occurring in oestrous (spontaneous or oestrogen-induced) and non-receptive does than in pseudopregnant or ovariectomized animals. If ovariectomized rabbits were pretreated with oestrogen, the pituitary response to LH-RH was restored. These findings suggest that there is little change in pituitary sensitivity to LH-RH infusion between oestrous and non-receptive rabbits, although pseudopregnancy (high physiological levels of progesterone) or ovariectomy inhibit its ability to respond to a releasing-hormone stimulus.     

Plasma concentrations of testosterone and LH in the male dog

Blood samples were withdrawn every 20 min from 3 conscious intact and 2 castrated mature males during non-consecutive periods of 12 h during the light and dark phases of the lighting schedule (intact dogs) and of 11 h during the light period (castrated dogs). In the intact dogs testosterone concentrations ranged from 0.4 to 6.0 ng/ml over the 24-h period. LH concentrations varied from 0.2 to 12.0 ng/ml. In all animals, LH peaks were clearly followed, after about 50 min, by corresponding testosterone peaks, but no diurnal rhythm could be established. LH concentrations in the castrated dogs were high (9.8 +/- 2.7 (s.e.m.) ng/ml), and still showed an episodic pattern in spite of the undetectable plasma testosterone levels.     

Studies of hormone secretion in romney rams: Luteinizing hormone,testosterone and prolactin plasma profiles,LH/testosterone interrelationships and the influence of seasons

In a study of hormone secretion patterns in rams remote sampling techniques were utilized for collecting jugular blood samples each 20 min for 24 h from adult Romney rams. Five animals were sampled during the summer, four during the winter, and plasma LH, testosterone and prolactin levels were estimated by specific radioimmunoassays.     

Blockade of pulsatile LH, FSH and testosterone secretion in rams by constant infusion of an LHRH agonist

Adult Soay rams were infused for 21 days with 50 micrograms buserelin/day, using s.c. implanted osmotic mini-pumps. The continuous treatment with this LHRH agonist induced a supraphysiological increase in the blood concentrations of LH (15-fold) and testosterone (5-fold) followed by a decrease below pre-treatment values after 10 days. The blood concentrations of FSH showed only a minimal initial increase but the subsequent decrease was dramatic, occurring within 1 day. By Day 10 of treatment, the blood concentrations of all 3 hormones were low or declining, LH pulses were absent in the serial profiles based on 20-min blood samples and the administration of LHRH antiserum failed to affect the secretion of LH or testosterone. By Day 21, the secretion of FSH, LH and testosterone was maximally suppressed. The i.v. injection of 400 ng LHRH was totally ineffective at stimulating an increase in the blood concentrations of LH while the i.v. injection of 50 micrograms ovine LH induced a normal increase in the concentrations of testosterone; this confirmed that the chronic treatment with the LHRH agonist had desensitized the pituitary gonadotrophs without markedly affecting the responsiveness of the testicular Leydig cells. The ratio of bioactive: radioimmunoactive LH did not change during the treatment. The long-term effect of the infusion was fully reversible as shown by the increase in the blood concentrations of FSH, LH and testosterone and the return of normal pulsatile fluctuations in LH and testosterone within 7 days of the end of treatment.     

Effects of season on the secretion of LH and testosterone in intact and castrated red deer stags (Cervus elaphus).

At 2--4 monthly intervals during the year blood samples were collected every 15 min for 6 h from 2 intact and 3 castrated red deer stags to study the relationship between season and the secretion of LH and testosterone. In the intact stags plasma LH and testosterone concentrations changed during the year; the LH levels were maximal in August during the phase of testicular redevelopment, while the testosterone levels were maximal from September to November coinciding with the time of peak testicular activity and the mating season. The castrated stags had higher plasma levels of LH than the intact stags at all times of the year, and there was no clear seasonal cycle in LH levels in these animals.     

Serum FSH, LH and testosterone in the male rhesus following prostaglandin injection.

Adult male rhesus were treated with PGE2, PGF2 alpha or the 13,14-dihydro-15-keto metabolite of PGE2 in a randomized crossover design. Serum concentrations of FSH, LH and testosterone were determined and compared to the respective values in the same uninjected animals. No significant changes were noted in controls or following the metabolite injection. FSH increased gradually for 4 hours after metabolite treatment. In contrast, injection of PGF2 alpha was followed by an abrupt (within 15 minutes) increase in LH and testosterone. FSH increased gradually in 2 of 3 treated animals. Injection of PGE2 was followed by a similar abrupt increase in LH concentration. This was not always associated with a significant increase in testosterone or FSH. These results demonstrate that injections of PGE2 or PGF2 alpha can change serum gonadotropin and testosterone concentrations in male rhesus monkeys, and that the effects of these two prostaglandins are qualitatively different.