Alterations in the proestrous pattern of median eminence LHRH, serum LH, FSH, estradiol and progesterone concentrations in middle-aged rats

The purpose of the following study was to assess the changes in the proestrous hormone profile in middle-aged cycling rats to better understand the inter-relationship and possible interaction of these hormones during the transition to estrous acyclicity. Median eminence LHRH concentrations and serum LH, FSH, estradiol and progesterone concentrations were measured in young (3-4 months old) and middle-aged (8-10 months old) proestrous rats at 0900, 1200, 1500 and 1800h. The data demonstrate that (1) baseline hormone concentrations prior to the surge at 0900h are the same in middle-aged and young rats; (2) the proestrous gonadotropin surge is temporally delayed in middle-aged rats; (3) this delay is preceded by lower median eminence LHRH concentrations and serum estradiol concentrations at 1200h; (4) serum progesterone concentrations are lower in middle-aged rats during the preovulatory gonadotropin surge (at 1500 and 1800h) probably as a consequence of the delayed LH surge.     

Rhythms in the ovulatory cycle. 2nd: LH, FSH, estradiol and progesterone

The circadian profiles of LH, FSH, estradiol and progesterone were compared in a homogeneous group of 15 young normally cycling women, at 4 well characterized times of the menstrual cycle: early follicular (EF), late follicular (LF), early luteal (EL) and late luteal (LL) stages. The circatrigintan profiles of the same hormones were also evaluated. Population-mean cosinor analysis failed to demonstrate a circadian periodicity of LH in any of the 4 stages of the menstrual cycle; a circadian rhythm for FSH was present only in the 2 luteal phases (EL, LL); the same type of rhythmicity was present for estradiol only in the late luteal stage; on the contrary, a highly significant circadian rhythm of progesterone was present in each of the 4 menstrual stages considered (EF, LF, EL and LL). Population-mean cosinor analysis showed a highly significant circatrigintan periodicity of LH and FSH with the acrophases respectively between -109 degrees and -181 degrees and between -74 degrees and -125 degrees. Circatrigintan rhythmicity was also present for estradiol (acrophases between -161 degrees and -245 degrees) and progesterone (acrophases between -246 degrees and -296 degrees).     

Effect of zearalenone and estradiol benzoate on serum concentrations of LH, FSH and prolactin in ovariectomized gilts

Six ovariectomized gilts were given zearalenone (Z), estradiol benzoate (EB) or vehicle in a replicated 3 x 3 Latin square design. Zearalenone was added to 2.3 kg of a corn-soybean ration at a dose of 1 mg Z/kg body weight; EB was given intramuscularly at 0.1 mg EB/kg body weight. Control gilts received vehicle solvent for both Z and EB. Blood samples were collected from indwelling jugular cannulas at 6-h intervals for 48 h before Z, EB or vehicle was given. After treatment, blood samples were drawn at 6-h intervals for an additional 84 h. Serum concentrations of luteinizing hormone (LH) decreased (P<0.001) from 4.67 ng/ml to 0.29 ng/ml within 6 h of EB. From 54 to 84 h after EB, serum concentrations of LH rose to 15.60 ng/ml (P<0.001). Serum concentrations of LH were reduced (P<0.001) in a similar pattern after Z (3.70 ng/ml to 0.49 ng/ml), but a rise in serum LH was not observed 54 to 84 h after Z (1.30 ng/ml). Serum concentrations of LH remained unchanged (P=0.55) in gilts given vehicle. Serum concentrations of follicle stimulating hormone (FSH) were suppressed (P<0.03) at 6 h in EB (19.10 vs 11.35 ng/ml) and Z gilts (16.16 vs 11.41 ng/ml) but remained unchanged in vehicle gilts. Serum concentrations of FSH did not change in EB or Z gilts during the next 36 h. These data indicate that the suppressive action of Z on serum concentrations of LH and FSH was similar to that of EB, while the biphasic stimulatory effect of EB for LH was not manifested by Z.     

Effects of estradiol and progesterone on circulating LH and FSH secretion,and ovarian antral follicle growth in anestrous ewes

In the ewe, ovarian antral follicles emerge or grow in a wave-like pattern and each wave is preceded by a peak in the serum FSH level. The purpose of the current study was to investigate whether in anestrous Western White Face ewes, a combination of progesterone and estradiol affects the circulating FSH peak secretion and the number of small ovarian follicles. Five ewes were treated with subcutaneous silastic rubber implants (10 cm × 0.47 cm), containing 10% estradiol-17β w/w (controls) and 5 ewes were treated with the same estradiol implant, along with subcutaneous implants (11 cm × 0.48 cm) containing 10% progesterone w/w for 12 days. Daily transrectal ovarian ultrasonography and blood sampling was performed from 5 days before, to 9 days after the period of implantation. Blood samples were also taken every 12 min for a 6 h period on day −2, 6 and 13 prior to or after implant insertion (day 0, day of implant insertion). Pulsatility in the serum LH levels was eliminated by the implants (P < 0.05). During the implantation period, the serum FSH peak amplitude was lower in ewes treated with implants releasing estradiol and progesterone, compared to ewes treated with implants releasing only estradiol (P < 0.05). No follicular waves emerged during implant treatment in both groups (P < 0.05) and the number of serum FSH peaks did not differ during implantation, compared to before implantation. During the implantation period, the number of small follicles did not differ in ewes with implants releasing estradiol and progesterone, compared to ewes treated with implants releasing only estradiol. To conclude, supra-physiological concentrations of estradiol completely eliminated the serum LH pulsatality and suppressed the follicular wave emergence, while the FSH secretory peaks that preceded the follicular waves were not affected. Supra-physiological concentrations of estradiol-17β with physiological concentrations of progesterone decreased the serum FSH peak amplitude, eliminated the serum LH pulses, but did not decrease the size of the small follicle pool in anestrous ewes.     

Effect of progesterone, administered via intravaginal rings, on serum concentrations of oestradiol, FSH, LH and prolactin in women

Intravaginal rings containing progesterone were inserted on Day 5 of the cycle to 8 healthy, normally menstruating women. Blood samples were taken during Days 4--22 of the cycle at 2--3-day intervals. The plasma progesterone levels obtained after the insertion were between 7.5 and 21 nmol/l. Four subjects showed no increase in plasma oestradiol concentrations. The subjects showing increased plasma oestradiol levels also showed a positive feedback on LH, resulting in ovulation or an LH peak. The results suggest that progesterone may have a local inhibitory effect on the follicular oestradiol production.     

Post partum patterns of circulating FSH, LH, prolactin, estradiol, and progesterone in nonsuckling cynomolgus monkeys.

Circulating levels of FSH, LH, prolactin (Prl), estradiol (E), and progesterone (P) were determined by RIA in four intact and four monkeys luteectomized (CLX) at parturition in order to a) characterize the patterns of these hormones during the puerperium, and b) examine a possible inhibitory role of the "rejuvenated" corpus luteum (CL) on the resumption of follicle growth post partum. In both groups during the first four weeks, FSH and LH were at tonic levels typical of ovulatory cycles. Recurrent puerperal "surges" of FSH, but not LH, unaccompanied by increments in serum E, were observed in both intact and CLX monkeys. No consistent pattern of serum Prl was apparent. CLX was followed by a prompt fall in serum P levels, which were elevated above typical follicular phase levels into the second week post partum in intact monkeys. Menstrual cycles resumed 2-4 months after delivery. Hormonal patterns during the first menstrual cycle post partum were indistinguishable from those observed in pregravidic ovulatory cycles. The findings indicate that in nonsuckling cynomolgus monkeys a) although it secretes progesterone, the puerperal CL does not inhibit the resumption of the ovarian cycle post partum, b) the puerperal ovary is not absolutely refractory to gonadotropins, since initial trials with Pergonal + hCG stimulated ovarian function, and c) ovarian activity during the puerperium may be limited by factors other than the tonic supply of gonadotropins.     

FSH and LH concentrations in periparturient mares.

The influence of the ovaries and presence of a foal on periparturient concentrations of FSH and LH were studied in 19 Pony mares. In intact and ovariectomized mares, mean concentrations of FSH fluctuated between 1.1and 9.9 ng/ml on Days -14 to-1 before parturition (Day 0). A surge of FSH occurred in all mares in association with parturition. From Days 1 to 10, the high levels of FSH gradually decreased in the intact group to the minimal concentrations that occur during oestrus, but remained elevated in the ovariectomized mares. There were no significant pre-partum changes in LH in either type of mare. Post-partum changes in LH concentrations increased at a similar rate in ovariectomized and intact mares. The presence of a foal significantly lengthened the interval to first oestrus, depressed LH levels on Days 6--10 and decreased the FSH concentrations as averaged over the 10 days before the first ovulation after parturition.     

Time-course relationships between serum LH, serum progesterone and urinary preganediol concentrations in normal women

A specific and sensitive gas chromatographic method was used to investigate the concentration of pregnanediol glucuronide in urine in relation to the time of ovulation. Serum LH and progesterone concentrations in the same subjects were used as evidence for the occurrence of ovulation. The urinary concentration of pregnanediol glucuronide in 24-hour collections and in overnight specimens increased 2-fold or more from the day of the midcycle LH peak to the time of predicted ovulation (24-48 hour after the LH peak) in parallel with the rise in serum progesterone concentration.     

Effects of estradiol, progesterone, and norethisterone on regional concentrations of galanin in the rat brain.

Concentrations of immunoreactive galanin were compared in eight gross brain regions of ovariectomized female rats treated with either estradiol, estradiol + progesterone, estradiol + norethisterone, or placebo. Higher concentrations with estradiol treatment compared with placebo were found in the pituitary (357%), frontal cortex (162%), occipital cortex (174%), hippocampus (170%), and median eminence (202%). A more profound difference with addition of progesterone or norethisterone was seen in the pituitary (529% and 467%, respectively). Sex steroids, particularly estradiol, modulate galanin concentrations not only in reproductive, but also in nonreproductive, brain regions.     

Ovarian dynamics, serum estradiol and progesterone concentrations during the interovulatory interval in goats

Ovarian changes determined by daily transrectal ultrasonic scanning, and its correlation with serum progesterone (P4) and estradiol (E2) concentrations were studied in seven cyclic Saanen goats. Estrous cycles were synchronized with 2 injections of a PGF2 alpha analogue 9 d apart. All follicles > or = 2 mm in diameter and CL were measured each day. One goat showed a longer interestrous interval, associated with development of a cystic-luteinized structure. The mean interovulatory interval for the other 6 goats was 20.8 +/- 0.4 d. The incidence of goats with 4, 3, and 2 follicular waves was 3, 1 and 2 respectively; follicular waves emerged on Days 0.5 +/- 0.6, 7.2 +/- 0.7, 10.7 +/- 0.5 and 13.7 +/- 0.8 for Wave 1, 2, 3 and the Ovulatory wave, respectively. The largest follicle of Wave 2 was smaller (4.9 +/- 0.1 mm) than the largest follicles of Wave 3 (6.2 +/- 0.1 mm; P < or = 0.01) and of the Ovulatory wave (7.0 +/- 0.5 mm; P < or = 0.01), and tended to be smaller than the largest follicle of Wave 1 (6.3 +/- 0.6 mm; P < or = 0.09). Interval between emergence of Wave 1 and Wave 2 was longer than interval between emergence of Wave 2 and Wave 3 (7.3 +/- 0.9 d vs 4.0 +/- 0.4 d; P < or = 0.01), and between Wave 3 and the Ovulatory wave (3.8 +/- 1.1 d; P < or = 0.05). Two days before ovulation, the diameter of the ovulatory follicle was larger (P < or = 0.01) than the first subordinate follicle. Serum E2 concentrations increased from the day of ovulation (2.7 +/- 0.3 pg/mL) to Day 2 (7.6 +/- 0.9 pg/mL; P < or = 0.01), associated with the early-mid growing phase of the largest follicle of Wave 1, and then decreased to basal levels on Day 5 (P < or = 0.01) and peaked again (16.5 +/- 2.4 pg/mL) 2 d before ovulation. The CL were detected ultrasonically on Day 3 post ovulation and attained a mean maximum diameter of 13.5 +/- 0.8 mm between Days 8 and 14. The following characteristics were observed: 1) ovarian follicular development in goats is wave-like; 2) increased P4 concentrations may be promoting follicular wave turnover; 3) it is suggested that the presence of follicular dominance and the production of E2 are different among waves. While in Wave 1 and in the Ovulatory wave, follicular dominance is present and production of E2 is consistent, no changes in serum E2 concentrations were found in other stages of the interovulatory interval. In the intervening waves, no indicators of follicular dominance could be firmly documented.     

Effect of progesterone on basal LH and episodic LH and FSH secretion in heifers

Heifers between Days 6 and 10 of the cycle were allocated at random to groups of 8 and treated with (i) a 4% progesterone-releasing intravaginal device (PRID) + oestrogen capsule for 12 days; (ii) 4% PRID for 12 days; (iii) 20% PRID for 12 days; (iv) 4% for 14 days; or (v) 20% PRID for 14 days. Blood was obtained daily during treatment and at 2- or 4-h intervals for 72 h after removal of PRIDs. Some animals were sampled every 20 min for 4.676 h on the 3rd day after PRID insertion, and 1 day before and 36 h after removal of the PRID insertion, and 1 day before and 36 h after removal of the PRID. During progesterone treatment there was: (i) no correlation between concentrations of progesterone and LH within days; (ii) a significant negative correlation between progesterone and days (P less than 0.01) and also between progesterone and LH over days (P less than 0.01); (iii) the overall correlation co-efficient between LH and days was positive (P less than 0.05). The amplitude of LH or FSH episodes was not affected as progesterone concentrations declined during PRID treatment, but the number of LH (but not FSH) episodes was increased (p less than 0.01). After PRID removal, the amplitude of both LH and FSH episodes increased (P less than 0.01). We suggest that progesterone is part of a negative feedback complex on LH secretion in cattle and that this effect is apparently mediated through frequency of episodic LH release.     

On the correlation between FSH, LH and prolactin serum levels.

In 188 males FSH, LH, and prolactin serum levels determined from a single blood sample were found to be closely correlated. No correlation appeared to testosterone levels. The same correlation is observed, if serum levels of FSH, LH, and prolactin are measured after stimulation with LH-RH and TRH. In order to explain the close correlation, in five young men hormone levels were measured at 2-min-intervals over a period of 2 hours. Peaks of prolactin often correspond to those of FSH and LH, and a statistical correlation was found in two cases between FSH and prolactin. Results suggest a common releasing mechanism, which is superposed to the main mediating mechanism.     

Effect of vascular cannulation on serum concentrations of LH, FSH, prolactin and cortisol in prepubertal gilts

Two experiments were conducted to determine whether cannulation of the jugular vein in gilts alters serum concentrations of LH, FSH, prolactin (PRL) or cortisol (C). In Experiment 1, 12 crossbred prepubertal gilts weighing 95 +/- 1.3 kg were immobilized by snaring, and tygon tubing was threaded into the anterior vena cava through a 12-gauge needle inserted into the jugular vein. Five hours later, blood samples were drawn at 20-min intervals for 4 h (Day 0). Samples were also drawn at 20-min intervals for 4-h periods 24 h (Day 1) and 48 h (Day 2) after cannulation. Serum concentrations of LH were similar (P=0.26) among Day 0 (0.40 ng/ml), Day 1 (0.39 ng/ml) and Day 2 (0.34 ng/ml). Serum PRL was similar (P=0.07) among Day 0 (4.10 ng/ml), Day 1 (3.87 ng/ml) and Day 2 (3.43 ng/ml). Serum concentrations of C were greater (P < 0.001) on Day 0 (8.32 ng/ml) than Day 1 (4.48 ng/ml) or Day 2 (3.54 ng/ml). In Experiment 2, cannulas were placed in 29 prepubertal gilts. Two days after initial cannulation, six blood samples were drawn at 20-min intervals. Gilts were then immobilized by snaring, and a second cannulae was inserted into the contralateral vein. Five blood samples were taken at 2-min intervals during the second cannulation and then six samples were drawn at 20-min intervals. Serum LH and FSH were not altered by cannulation or elevated during the subsequent 2-h sampling period (P>0.05). In contrast, serum concentrations of PRL rose slowly (P<0.05) during cannulation and remained elevated for 60 min before returning to baseline. Serum concentrations of C rose within 6 min of cannulation, remained elevated for 30 min, and then declined over the next 90 min. From these two experiments, it appears that secretory patterns of LH and FSH can be accurately assessed immediately after cannulation in prepubertal gilts. Measurements of serum PRL and C that reflect nonstressed conditions, however, cannot be obtained until at least 2 h or 1 d after cannulation, respectively.     

Short-term relationships between plasma LH, FSH and progesterone concentrations in post-partum dairy cows and the effect of Gn-RH injection

Jugular venous blood samples were obtained from 7 dairy cows every 10 min for 10-19 h during the early- or mid-luteal phase of the oestrous cycle, and each cow was given 1 or 2 i.v. injections of 100 micrograms synthetic Gn-RH. Four of these cows were also sampled in a different cycle with no treatment being administered. Peaks of plasma LH, FHS and progesterone were detected in each animal in the absence of treatment; those of LH and progesterone often occurred in parallel. Injection of Gn-RH was always followed by a significant increase in plasma LH and progesterone concentrations and in most cases by a significant FSH increase. There was a significant temporal relationship between the peaks of all 3 hormones. A further 8 cows were sampled during the first 10 days post partum when the mean plasma progesterone concentration was low. An i.v. injection of 200 micrograms synthetic Gn-RH was given to each animal and this resulted in a significant increase in plasma LH and FSH concentrations, but in only one cow was the Gn-RH injection followed by a significant increase in plasma progesterone concentration. The LH response to Gn-RH injection was significantly less in cows injected on or before Day 5 post partum than in cows injected on Days 7-10 post partum.