Elevated LH Values Research Articles

Reproductive performance of Zebu cattle in Mexico: 2. Seasonal influence on the levels of progesterone, estradiol-17β, cortisol and LH during the estrous cycle

Levels of progesterone, estradiol-17β, cortisol and LH were determined in 18 cyclic Zebu females during the rainy (n = 11) and the dry season (n=7). Four cows studied during the rainy season stopped cycling and were considered to be anestrous. Blood samples were collected from the animals once daily from Day 2 (day of estrus=Day 1) to Day 16, and three times daily from Day 17 to the day before the expected onset of estrus, when the frequency was increased to every 3 hours until ovulation. Increases in concentrations of progesterone were more pronounced in the rainy season (n = 7) than in the dry season (n = 7): on Days 4, 5 and 7 higher concentrations were found during the rainy season (P<0.1, P<0.05 and P<0.05 respectively). Decrease in the concentrations of progesterone started on Day −4 before the next estrus during the rainy season and on Day −3 during the dry season. The area under the curve of estradiol-17β from Day −3 to ovulation was greater during the rainy period than during the dry period (P< 0.05). In all animals, a peak of estradiol-17β was found around Days 4 to 7 of the cycle (n=14). In five animals, a second peak was detected around midcycle. A third peak was recorded on Day 18 (n=5). Levels of cortisol were higher during the rainy than the dry season (P< 0.05). The interval between the onset of estrus and the LH peak was 6.7 hours (n=5), while the interval between the LH peak and ovulation was 21.3 hours (n=8). In the dry period, three of the animals had significantly elevated LH values the day before the LH surge.

Neuroendocrine responses to exogenous estrogen: No differences between heterosexual and homosexual men

Plasma LH concentrations were determined in 55 men before and for four days following injection of 10 mg, 20 mg, or 30 mg Premarin or a placebo injection of vehicle. Testosterone (T) and dihydrotestosterone (DHT) concentrations were also determined in plasma samples taken just prior to Premarin or placebo injection and in samples taken three days later. All subjects provided self-descriptions of their sexual orientation and, based upon these descriptions, were classified as heterosexual (N=39) or homosexual (N=16). Premarin injection resulted in a reliable reduction in plasma LH 24 hr later. In subsequent samples, LH values rose and in many cases exceeded baseline levels, most reliably in those subjects receiving the 10 mg dose. Contrary to some previous reports, we observed no significant differences between heterosexual and homosexual subjects in the likelihood of their exhibiting elevated LH concentrations following exogenous estrogens. T, but not DHT, concentrations were suppressed after Premarin injection in both groups of subjects. Other than Premarin dosage, we could not identify any variable which predicted the likelihood of elevated LH values.

Limited responsiveness of LHRH neurons norepinephrine may account for failure of locus coeruleus or medullary A1 electrical stimulation to increase plasma LH in estrogen-treated ovariectomized rats

We recently reported that electrical stimulation (ES) of the locus coeruleus (LC) or the medullary A1 noradrenergic cell groups markedly increased LH secretion. However, these amplifying effects occurred only in rats in which preliminary electrochemical stimulation (ECS) of the medial preoptic nucleus (MPN) was performed. In contrast, ES of either LC or A1 alone did not alter basal LH secretion. Possible explanations for this dichotomy in LH response include: (1) LHRH neurons in unanesthetized, estrogen-treated, ovariectomized (OVX) rats are relatively unresponsive to NE, (2) the chloral hydrate anesthesia used in our brain stimulation studies elevates the threshold of excitability of LHRH neurons to norepinephrine (NE)_and/or pituitary responsiveness to LHRH, (3) preliminary MPN-ECS reduces thresholds of resposiveness of LHRH neurons to NE, and (4) the LHRH secreted after MPN-ECS sensitizes the pituitary gland to the subsequent small amounts of LHRH released following LC- or A1-stimulation. To provide answers to these questions, 3 experiments were performed in estrogen-treated OVX rats into which had been inserted the third ventricle and jugular cannulae. In the first study, the effects of artificial cerebrospinal fluid (ACSF) or ACSF + Ne (5,20, or 45 μg) on plasma LH concentrations in unanesthetized, unrestrained rats were examined. The intracerebroventricular (ICV) infusion of 5 μg of NE increased plasma LH by 61.3% above basal levels within 10 min whereas 20 or 45 μg NE elevated LH values 166.9 and 182.8%, respectively. The next study examined the effects of anesthetic drugs on LH response produced by ICV infusions of 45 μg of NE. Regardless of whether rats were anesthetized with ether, chloral hydrate, urethane, Saffan (alphaxolone + alphadolone) or ketamine + acepromazine, peak LH responses to ICV NE were not significantly different from unanesthetized controls. In a second study we observed that ICV NE (45 μg) markedly amplified and prolonged the release of LH after MPN-ECS. Moreover, the peak LH responses in these animals were approximately 10× greater than those obtained in rats which received ICV NE but not MPN-ECS. The third series of studies demonstrated that pituitary responsiveness to LHRH was not an important factor in dictating the LH response obtained after NE ICV infusions. These data suggest that LHRH neurons in estrogen-primed OVX rats are not particularily responsive to NE and that following MPN-ECS, LHRH neuronal responsiveness to this catecholamine markedly increases.

Testicular function in young men in long-term remission after treatment for the early stages of Hodgkin's disease.

16 young men in long-term remission after standard treatment for the early stages of Hodgkin's disease were examined for testicular function 48 to 125 months after termination of therapy. The patients had received mantle field irradiation, plus either irradiation of infradiaphragmatic lymph nodes (7 patients) or 6 cycles of MOPP (9 patients). 5 patients had almost normal semen quality judged by seminal fluid analysis. 11 patients had reduced semen quality (8 severely reduced) and often elevated FSH values. Semen samples of poor quality were significantly more common in patients treated with MOPP (7/9) than in those treated with infradiaphragmatic irradiation (1/7). One patient showed signs of regeneration of spermatogenesis. None had experienced reduction in libido and sexual performance after therapy; correspondingly, none had below normal testosterone values or elevated LH values. Patients should be informed about the risk of infertility before treatment. If in a given case several treatment options with equal prospective antineoplastic effect are weighed against one another, the patient's possible desire to retain fertility should favour the use of radiotherapy as opposed to chemotherapy, especially including alkylating agents.

Evidence for Seasonal and Nutritional Modification of Ovarian and Pituitary function in Crossbred Heifers and Brahman Cows2,3

Alterations in endocrine response in the bovine female after consumption of monensin or exposure to changes in season were observed in two experiments. Thirty-three monensin-fed (M) or control (C) crossbred heifers in Exp. 1A were given a porcine follicle stimulating hormone (FSH-P) challenge on d 16 to 21 postestrus. Nine M heifers ovariectomized (OVX) on d 11 after the FSH-challenged estrus had a greater number of smaller corpora lutea (CL; P less than .005) than did nine d 11 OVX C heifers. Serum progesterone (P4) concentrations were greater in M on d 5 through 13 following the FSH-challenged estrus (P less than .001). Seven M and seven C Brahman cows in Exp. 1B given an identical FSH challenge had similar increases in CL number and size. In Exp. 2, blood samples were obtained from 14 M and 13 C Brahman cows during winter (WI), early spring (ESp) and late spring (LSp) to characterize the preovulatory LH surge. During each seasonal period, blood samples were taken hourly from estrus through 24 h postestrus for each cow. Only one of five WI-C cows had a preovulatory LH surge compared to five of five WI-M cows (P less than .01). No differences were found in the number of cows having an LH surge in ESp or LSp groups. Analysis of combined WI and ESp group values indicated a difference in timing of the LH surge by M or C treatment. Of those cows that had an LH surge, only three of 10 C had peak LH values later than the first sample taken, compared with 10 of 15 M (P less than .10). A heightened LH response was detected in M cows in all comparisons of LH surge profiles (P less than .005). Concurrent with changes in season from WI to ESp was an increase in number of C cows having an LH surge (one of five vs nine of 10; P less than .005), and elevated LH values in ESp-C and M groups compared with WI-C and M groups (P less than .05). Midluteal blood samples taken after every estrus indicated P4 to be greatest in February M cows (P less than .10) and P4 tended to be greater in February and lower in January for all groups. Conclusions are that monensin affects the FSH-P-induced ovulation rate of bovine females of all ages. Seasonal effects occurring between the shortest and longest days of the year exert their greatest influence on the preovulatory LH surge and P4 concentrations in Brahman cows between January and March. Seasonal effects appear to be partially modulated by nutritional factors.

The effect of intraventricular gamma aminobutyric acid (GABA) on hypothalamic catecholamines and LHRH and on pituitary hormone release

The present experiments were designed to evaluate the role of catecholamines in mediating the actions of GABA on pituitary hormone release following its intraventricular injection. GABA was administered intraventricularly, at doses of 0.1 and 4 μMol, to chronically ovariectomized rats. Five and 15 min after intraventricular injection, the animals were sacrificed by decapitation. Blood was collected for LH and PRL determination by RIA, and brains were frozen for subsequent determination of LHRH by RIA, and dopamine (DA) and norepinephrine (NE) by radioenzymatic assay. Brain areas analyzed included the median eminence (ME), medial basal hypothalamus (MBH) and suprachiasmatic-medial preoptic area (Sch-PO). Controls received an equal volume (2 μl) of saline. As previously observed, GABA had opposite effects on prolactin (PRL) release depending on the dose employed. A decline in serum PRL was induced by a low (0.1 μMol) dose, whereas a larger (4 μMol) dose induced an increase in PRL levels. LH levels were increased only with the 4 μMol dose. The elevated LH values were paralleled by an increase in LHRH levels in the Sch-PO region 15 min after GABA. Marked changes in catecholamines, particularly in DA, were seen after GABA injection. Significant increments in DA levels in the ME were seen 5 and 15 min after the 0.1 μMol dose of GABA. Similarly, this low dose of GABA induced a marked increase in DA levels in the anterior-pituitary (AP) gland at 15 min. No changes in DA were seen in either MBH or Sch-PO areas. The 4 μMol dose of GABA induced only a small increase in AP levels of DA, without altering the amine levels in any of the brain areas examined. NE levels in the ME were elevated 5 min after the administration of either dose of GABA. No changes in NE were seen in either the MBH or Sch-PO areas. These results indicate that intraventricular GABA injection not only alters pituitary hormone release but also release of DA and NE from terminals in the ME. The released catecholamines may be important in mediating the effects of GABA on releasing factor discharge. In addition, the DA released may have acted directly on the AP to inhibit release of PRL.

Radioimmunoassay of luteinizing hormone in the blood of Zebu cattle.

Summary. A solid-phase radioimmunoassay was used to measure lh in the serum of a Zebu cow and heifer during the oestrous cycle. Shortly after the onset of oestrus, serum levels of lh rose sharply to 20 to 120 ng/ml before dropping to baseline levels of about 2 ng/ml after 8 to 10 hr. Elevated lh values were also detected in mid-cycle, although considerable variation in activity over several days occurred with the heifer. Peak values of lh were considerably higher in the serum of the cow than the heifer.