Changes In Estrogen Levels Research Articles

The Hypothalamic-Pituitary Axis of Streptozotocin-Induced Diabetic Female Rats is Not Normalized by Estradiol Replacement*

Studies in diabetic rats have found abnormalities at the hypothalamic, pituitary, and/or ovarian level but have not controlled for changes in estrogen levels induced by diabetes. The purpose of this investigation was to study the effect of diabetes on the hypothalamic-pituitary axis in ovariectomized rats treated with estradiol (E2). Ovariectomized 60 day old female rats were assigned to control (C, n = 42), diabetic (D, n = 47) or insulin-treated diabetic (DI, n = 16) groups. Diabetes was induced with an injection of streptozotocin in the D and DI groups. In the C, D, and DI groups, estrogen was replaced by implanting blank, 5 micrograms or 20 micrograms E2 pellets sc. Pituitary LH responsiveness to GnRH was assessed in C and D animals. Anterior hypothalamic and midhypothalamic concentrations of proGnRH and GnRH, pituitary LH and FSH and serum levels of LH, and E2 were measured by RIA. Anterior hypothalamic proGnRH concentrations were decreased in diabetic rats treated with 5 micrograms E2 compared to 5 micrograms E2 control animals (P less than 0.05). Midhypothalamic GnRH concentrations were also reduced in D vs. C animals despite comparable estrogen therapy (P less than 0.004). GnRH-stimulated LH levels were greater in E2-treated diabetic females than in similarly treated control rats (P less than 0.001). D and DI animals were more sensitive than controls to the inhibitory effect of estrogen on basal LH levels. Pituitary LH and FSH content was lower in 20 micrograms E2-replaced animals but was not influenced by the diabetic state. These data demonstrate a diabetes-induced decrease in hypothalamic proGnRH and GnRH concentration which is not corrected with E2 replacement. The hyper-responsiveness of the diabetic rat pituitary to GnRH also suggests a chronic lack of GnRH stimulation from the hypothalamus but a continued ability of the pituitary to respond to GnRH.

7 Endocrine control of plasma lipoprotein metabolism: effects of gonadal steroids

Gonadal steroids are powerful modulators of plasma lipoprotein metabolism. In general, steroids with oestrogenic activity increase plasma levels of HDL, especially HDL2, and reduce levels of LDL. Steroids with androgenic activity have opposite effects, consistent with the sex difference in HDL and LDL levels. Triglyceride levels are lowered by exogenous administration of androgens and are raised by oral oestrogens, contrary to the observed sex difference in this lipid. The impact of administered gonadal steroids is modified by factors such as dosage and chemical structure, with synthetic steroids having a more pronounced effect than natural hormones. The effects of these steroids may depend on the pre-treatment lipoprotein pattern and endocrine status, and are modified by the route of administration, with oral hormones often having greater metabolic effects than those given parenterally. The net effects of oestrogen and progestagen combined preparations on lipoprotein metabolism depends on the balance between oestrogenic and androgenic activity. In contrast, endogenous changes in sex hormone levels, such as those accompanying puberty, the menstrual cycle and the menopause, have relatively little effect on plasma lipoproteins. Data concerning puberty and castration in males indicate that testosterone is a key factor in the sex difference in HDL levels. There is evidence that loss of ovarian function induces significant increases in LDL level, but endogenous changes in oestrogen levels have little effect on HDL metabolism in women. Changes in triglyceride levels are due mainly to alteration in VLDL secretion and catabolism. LDL levels are controlled by the activity of B100, E receptors and, to a lesser extent, changes in LCAT activity. Gonadal steroids affect HDL levels by altering apoAI synthesis and by controlling the activity of hepatic lipase. Lp(a) levels are increased during early pregnancy but may be decreased by anabolic steroids. The mechanisms behind such actions are unknown. Gonadal hormones influence all areas of plasma lipoprotein metabolism and therefore may affect cardiovascular risk by favourably affecting the plasma lipoprotein profile. In postmenopausal women, use of oestrogens has led to a 60% reduction in cardiovascular disease (Bush et al, 1987). Androgens and progestagens with androgenic properties induce changes in plasma lipoproteins which may increase risk. Further study of the mechanisms involved in these changes is obligatory given the widespread use of these hormones.

Growth and differentiation of teratocarcinoma OTT6050 affected by host hormonal changes in old mice.

We previously reported the age and sex dependent decrease in the growth rate of teratocarcinoma OTT6050. Studies of the effects of hormones on the tumor growth are presented here. Age related changes in the serum levels of triiodothyronine, thyroxine, progesterone, testosterone and estradiol that increase in the young adult and decrease in the old were observed with radioimmunoassay. Administration of estradiol to tumor-bearing, 50 week-old female mice increased the tumor growth rate to that of 10 week-old mice. Tumor growth rates in estradiol-treated 10 week-old female and male mice were slightly accelerated compared to the control, but not as fast as that of control juveniles. It can be concluded that extrinsic estradiol stimulates the teratocarcinoma growth in vivo especially in old female mice. Age-dependent decline of the growth rate of teratocarcinoma in the female is due partly to changes in estrogen level.

Plasma estrogen levels during pregnancy in the western spotted skunk.

The present study was undertaken to obtain an estrogen profile throughout gestation in the western spotted skunk with special emphasis on relating changes in estrogen levels to blastocyst development. Blood samples were collected from 130 pregnant animals by cardiac puncture and plasma estrogen levels were determined by radioimmunoassay (RIA). Estrogen levels varied throughout the period of embryonic diapause, with mean levels ranging between 3 to 18 pg/ml. There was a tendency for estrogen levels to be less variable and somewhat lower during the 15 days immediately prior to blastocyst implantation than during the preceding period. Plasma estrogen levels in skunks with delayed implanting blastocysts (diameters of 1.1 mm or less) were significantly higher (P less than 0.05) than those in females with activating blastocysts (i.e., diameters of 1.2 mm or greater), again suggesting that estrogen levels were reduced during the period immediately preceding implantation. However, the exact physiological significance, if any, of this modest reduction in estrogen levels remains to be determined.

Status migrainosus: causative and therapeutic aspects.

SYNOPSISBecause of the scarcity of information on Status Migrainosus (SM), the members of the AASH were surveyed as to (1) precipitating factors; (2) criteria to hospitalize patients; and (3) initial, (4) second‐line, (5) adjunct, and (6) follow‐up modes of therapy for SM. SM was defined as a disabling migraine headache of 72 hours duration that was refractory to usual treatment. Of 540 AASH members polled, 126 responses were received from physicians. As to precipitating events, psychiatric factors, medication abuse and withdrawal, diet, and changes in estrogen levels were mentioned most often and in that order. The major criteria to hospitalize included intense pain, nausea, vomiting, psychiatric factors, and suspicion of neurologic disease. While the therapeutic approach to SM varied; antiemetics, narcotics, prophylactic agents, ergot compounds, steroids and sedation were most often mentioned. Responses regarding follow‐up measures listed prophylactic medication, supportive psychotherapy, patient education, and rapid symptomatic therapy as the major means to prevent recurrence.

Temperature and heat flow variations during the menstrual cycle: Breasts and extremeties

1. 1. The mid-menstrual cycle breast temperature ( T Br) peak in women earlier described by Nassar & Smith (1975) has been more closely evaluated and compared with menstrual cycle variations in other peripheral regions. 2. 2. Alignment of the T Br, heat flow and conductance data by the day of the T Br peak showed a significant rise and fall in these three variables, the peak occurring 2–4 days prior to the estimated day of ovulation and the nadir usually within 1 day of estimated ovulation. The relative changes in these data during the mid-cycle peak proved significant and distinguished it from other cyclic variations or elevations later in the cycle. This phenomenon was not found to occur at peripheral areas of the arm, thigh, calves and forehead. 3. 3. Rectal temperature ( T Re) remained stable at the time of the T Br peak, with a slight elevation following estimated ovulation. 4. 4. Progesterone assays clearly indicated the occurrence of ovulation in 70% of the subjects studied. 5. 5. It is noted that the T Br pattern very closely resembles that of plasma oestradiol levels established for humans during the menstrual cycle, and it is hypothesized that the breast thermal response is due to cyclic changes in oestrogen levels leading to an increase in blood flow to that area.

Heart period variability during estrogen exposure and withdrawal in female rats

Heart period, heart period variability, and an estimate of vagal tone were evaluated during estrogen exposure and withdrawal in ovariectomized, freely moving female rats. Spectral analysis was used to quantify the respiratory component of heart period variability (V̂), which has been found to be sensitive to alterations of vagal tone to the heart. During estrogen withdrawal, V̂ decreased significantly and was accompanied by a decrease in heart period. There were no significant differences in heart period or V̂ between the experimental (estrogen) group and the control (no estrogen) group during estrogen exposure. Total heart period variability did not differ significantly from controls during estrogen withdrawal but it did exhibit an increase during estrogen exposure. In this experiment V̂ appeared to be more sensitive to changes in estrogen levels than total heart period variability. These data suggest that decreases in cardiac vagal tone and heart rate occur during estrogen withdrawal.

The effect of hepatic interposition on ovary-pituitary interaction.

When the livers of female rats were provided with exclusive first access to all ovarian venous effluents by simultaneous castration and implantation of a portion of one of the ovaries beneath the splenic capsule, systemic venous plasma concentrations of estrone and estradiol were reduced 40%. Paradoxically, progestins in the peripheral plasma increased threefold, most probably because of augmented adrenocortical progestin secretion. Nevertheless, the change in estrogen levels alone was sufficient to abolish trophic effects on the genital organs and to block normal inhibition of pituitary gonadotropin secretion. Plasma gonadotropin concentrations were markedly elevated to levels comparable to those of castrates, and, as a result, the intrasplenic ovarian implants grew excessively and became histologically disorganized. A patent portacaval shunt negated the entire process, providing proof that the measured hormonal alterations and the change in the implant itself were direct consequences of hepatic screening.

CHANGES IN BLOOD COAGULATION PROFILES OF DAIRY COWS DURING PREGNANCY AND IN HEIFER CALVES AFTER HORMONE TREATMENT

Blood coagulation profiles were determined throughout pregnancy in dairy cows. Unlike the pregnant human female or the pregnant bitch, the bovine coagulation profiles remained relatively constant throughout pregnancy and showed little change in response to the changes in plasma levels of estrogen and progesterone which occur during pregnancy. While there was a tendency for the platelet count to decrease and the plasma fibrinogen levels to increase during pregnancy, the levels of specific coagulation Factors VIII and XI remained constant and Factors VII and IX showed an increase in some animals but not in others. The changes in coagulation profiles of heifer calves after treatment with progesterone and estrogen alone and in combination were similar to those observed during pregnancy.

Plasma levels of specific coagulation factors and oestrogens in the bitch during pregnancy.

ABSTRACTDuring pregnancy in twelve bitches a significant increase was observed in the circulating activity of the specific coagulation factors VII, VIII, IX and XI. Such changes did not occur in two bitches which were bred but did not conceive. Comparison of the plasma procoagulant activity and oestradiol‐17β levels indicated that alterations in the coagulation factor activity may, at least in part, be mediated by the changes in oestrogen levels which occur in the pregnant bitch.

Temporal changes in circulating steroids during prostaglandin F 2α induced abortion in the rat and rabbit

The serum levels of progesterone ( Δ 4P), 20α-dihydroxyprogesterone (20α-DHP), pregnenolone ( Δ 5P) and estrogens at different time intervals during Silastic-PVP-PGF 2α tube induced midterm abortion were measured by radioimmunoassay in the rat and rabbit. The concentrations of 4P and Δ 5P were significantly reduced but that of 20α-DHP was increased significantly as early as 20 hours after PGF 2α treatment. Estrogen levels showed slight reduction in the rat but remained unchanged in the rabbit. The ratio of Δ 4P/20 α-DHP recorded were 2.15 and 16.86 (pretreatment) and dropped to 0.08 and 0.37 (60 hours after insertion of Silastic-PVP-PGF 2α tube) in the rat and rabbit, respectively. These findings suggest that the suppression of circulating Δ 4P by PGF 2α might be the result of a reduced precursor ( Δ 5P) pool size as well as changes in the enzymic systems responsible for the formation and conversion of Δ 4P. It is still to be determined if changes in estrogen levels in the rat have any bearing on abortion induced by PGF 2α.

Changes in estrogen levels in maternal venous plasma after intra-amniotic infusion of Prostaglandin F 2α for therapeutic abortion

Peripheral plasma levels of estrone, estradiol-17β and estriol were measured in 10 women following the intra-amniotic infusion of prostaglandin F 2α (PGF 2α) for therapeutic abortion. The PGF 2α was given between the fourteenth and twentieth weeks of gestation and the mean induction-abortion interval (± S.D.) was 24 ± 12 hours. It was found that the mean estrone, estradiol-17β and estriol levels fell to about half of the pre-infusion levels after 80% of the induction-abortion interval had elapsed. The main decline in estrogen levels usually occurred in individual women either during the first quarter or during the last quarter of the induction-abortion interval. No relationship could be demonstrated between the changes in estrogen levels and the interval from first administration of PGF 2α to subsequent abortion.

Plasma oestrogen levels in rainbow trout Salmo gairdneri Richardson

Levels of oestrogens in plasma of mature fall‐spawning rainbow trout Salmo gairdneri were determined using a radio‐immunoassay. No significant difference was found in oestrogen concentration between the sexes (male x̄=2.5 ng/ml; female x̄=4.4 ng/ml); between individual variability was great. Four blood samplings over a 24‐h period via cardiac puncture of males revealed no diel variation or change in estrogen levels due to the stress of bleedings. Although no gonado‐somatic index‐estrogen relationship could be demonstrated for either sex, there was correlation between oestrogen and androgen levels in the female.

ANTIBODIES AGAINST HORMONES

The use of steroid radioimmunoassay in studies of physiological processes the development of new methods of assaying gonadotropins and the use of antibodies to interfere with various physiological processes are discussed. Assays for estradiol and progesterone were made of more than 100 fluid samples collected from the Graafian follicles in human ovaries 3-6 hours before expected ovulation. Levels of the 2 steroids were highly correlated in samples from different tissues but concentrations varied considerably with some follicles containing more than 2 mcg/ml of estradiol. It is suggested that metabolic changes in human follicles may be similar to those occurring in rabbits. Radioimmunoassay to determine changes in prostaglandin F2alpha in relation to changes in estrogen levels indicated high prostaglandin levels associated with low levels of estrogens. A similar relationship has been observed in rabbits as ovulation approaches. A specific and sensitive assay for human follicle-stimulating hormone using an antisera which is incubated with luteinizing hormone and follicle-stimulating hormone to eliminate cross-reactivity and the 2-site assay technique is described. Studies of the action of antibodies against hormones particularly against gonadotropins steroids releasing hormones and prostaglandins are reviewed. The possible sensitization of the human female to the placental hormones HCG and HPL would result in the withdrawal of luteotrophic support of the corpus luteum and may thus constitute an immunological method of sterilization.