Gonadotropin, ACTH, prolactin, sexual steroid and cortisol levels in postmenopausal women's cerebrospinal fluid (CSF)

Neuroendocrinology of bone

The past decade has witnessed significant advances in our understanding of skeletal homeostasis and the mechanisms that mediate the loss of bone in primary and secondary osteoporosis. Recent breakthroughs have primarily emerged from identifying disease-causing mutations and phenocopying human bone disease in rodents. Notably, using genetically-modified rodent models, disrupting the reciprocal relationship with tropic pituitary hormone and effector hormones, we have learned that pituitary hormones have independent roles in skeletal physiology, beyond their effects exerted through target endocrine glands. The rise of follicle-stimulating hormone (FSH) in the late perimenopause may account, at least in part, for the rapid bone loss when estrogen is normal, while low thyroid-stimulating hormone (TSH) levels may contribute to the bone loss in thyrotoxicosis. Admittedly speculative, suppressed levels of adrenocorticotropic hormone (ACTH) may directly exacerbate bone loss in the setting of glucocorticoid-induced osteoporosis. Furthermore, beyond their established roles in reproduction and lactation, oxytocin and prolactin may affect intergenerational calcium transfer and therefore fetal skeletal mineralization, whereas elevated vasopressin levels in chronic hyponatremic states may increase the risk of bone loss.. Here, we discuss the interaction of each pituitary hormone in relation to its role in bone physiology and pathophysiology.

Neuropsychological complications of hypoprolactinemia

Prolactin (PRL) is primarily produced by the pituitary lactotrophic cells and while initially named for its role in lactation, PRL has several other biological roles including immunomodulation, osmotic balance, angiogenesis, calcium metabolism, and appetite regulation. Most of the PRL-related literature has traditionally focused on hyperprolactinemia, whereas hypoprolactinemia has received little attention. There is evidence to suggest that PRL receptors are widely distributed within the central nervous system including the limbic system. Furthermore, PRL has been shown to play key role in the stress regulation pathway. Recent data also suggest that hypoprolactinemia may be associated with increased sexual dysfunction, anxiety, and depression. In this paper we discuss the current understanding regarding the neuropsychological impact of hypoprolactinemia and highlight the need for adequately defining hypoprolactinemia as an entity and consideration for future replacement therapies.

Estropause, Sex Hormones and Metal Homeostasis in the Mouse Brain

Alterations in brain metal ion homeostasis have been reported with aging and are implicated in the pathogenesis of neurodegenerative diseases. To assess whether age-related changes in hypothalamic-pituitary-gonadal (HPG) hormones might be involved in modulating brain metal ion homeostasis, we treated 7.5-month intact, sham-ovariecomized and ovariectomized C57B6SJL mice with vehicle or leuprolide acetate (for 9-months) to differentiate between whether sex steroids or gonadotropins might modulate brain metal ion concentrations. Unlike other aging mammals, there was no increase in plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH) concentrations following estropause in mice, suggesting there was sufficient residual production by the follicle depleted ovary, of sex steroids like estrogens and protein hormones like the inhibins, in order to suppress pituitary LH/FSH production. Castration on the other hand induced significant increases in circulating LH and FSH. Modulation of plasma sex steroid and gonadotropin levels did not significantly alter the concentrations of brain metals tested (Fe, Zn, Cu, Mn, Co, Ni, Al, Li), although there was a tendency for a decrease in all brain metals following ovariectomy (low estrogens and progesterone, high gonadotropins), a response that was reversed with leuprolide acetate treatment (low sex steroids, low gonadotropins). Brain Cu concentration was the only metal correlated with plasma LH (−0.37, n = 30, p < 0.05) and FSH (−0.42, n = 29, p < 0.01). This study demonstrates that sex hormones do not markedly alter brain metal ion homeostasis, unlike previously reported studies of circulating metal ion homeostasis. The role of gonadotropins in regulating metal ion homeostasis does however warrant further study.

Weak correlations between serum and cerebrospinal fluid levels of estradiol, progesterone and testosterone in males

Background

Neuroactive steroids seem to be implicated in a variety of neurophysiological and behavioral processes, such as sleep, learning, memory, stress, feeding and aging. Numerous studies have also addressed this implication in various cerebral disorders and diseases. Yet, the correlation and association between steroids in the periphery, e.g. blood, and the central compartments, e.g. cerebrospinal fluid (CSF), have not yet been comprehensively assessed. As the brain is not directly accessible, and the collection of human CSF usually requires invasive procedures, easier accessible compartments, such as blood, have always attracted attention. However, studies in humans are scarce. In the present study we determined estradiol, progesterone and testosterone levels in CSF and serum of 22 males without cerebral disorders or diseases.

Results

Samples were taken under conditions corresponding closest to basal conditions with patients expecting only spinal anesthesia and minor surgery. All samples per patient were collected concomitantly. Total estradiol, progesterone and testosterone concentrations were measured by electro-chemiluminescence immunoassay. The strength of correlation was assessed by Spearman’s rank correlation coefficient. Correlation analysis revealed merely weak to very weak correlations for estradiol, progesterone and testosterone respectively between the CSF and serum compartments.

Conclusions

Total steroid levels of estradiol, progesterone and testosterone in CSF and serum of males without neurological disorders were determined. Weak to very weak correlations between CSF and serum were found thus suggesting that concentrations in the periphery do not parallel concentrations in the central compartments. Further research is needed to clarify to what extent and under which conditions serum levels of estradiol, progesterone and testosterone may possibly serve as a biomarker reflecting the respective concentrations in the CSF or in the brain.

The choroid plexus as a sex hormone target: Functional implications

The choroid plexuses (CPs) are highly vascularized branched structures that protrude into the ventricles of the brain, and form a unique interface between the blood and the cerebrospinal fluid (CSF). In recent years, novel functions have been attributed to this tissue such as in immune and chemical surveillance of the central nervous system, brain development, adult neurogenesis and circadian rhythm regulation. Sex hormones (SH) are widely recognized as modulators in several neurodegenerative diseases, and there is evidence that estrogens and androgens regulate several fundamental biological functions in the CPs. Therefore, SH are likely to affect the composition of the CSF impacting on brain homeostasis. This review will look at implications of the CPs' sex-related specificities.

Sex Hormone Decline and Amyloid β Synthesis, Transport and Clearance in the Brain

Sex hormones (SH) are essential regulators of the central nervous system. The decline in SH levels along with ageing may contribute to compromised neuroprotection and set the grounds for neurodegeneration and cognitive impairments. In Alzheimer's disease, besides other pathological features, there is an imbalance between amyloid β (Aβ) production and clearance, leading to its accumulation in the brain of older subjects. Aβ accumulation is a primary cause for brain inflammation and degeneration, as well as concomitant cognitive decline. There is mounting evidence that SH modulate Aβ production, transport and clearance. Importantly, SH regulate most of the molecules involved in the amyloidogenic pathway, their transport across brain barriers for elimination, and their degradation in the brain interstitial fluid. This review brings together data on the regulation of Aβ production, metabolism, degradation and clearance by SH.

Neuroactive steroids in periphery and cerebrospinal fluid

Some peripheral steroids penetrate the blood-brain barrier (BBB), providing at least substances for the CNS steroid metabolome. That is why the predictive value of the peripheral steroids appears to be comparable with that of the cerebrospinal fluid (CSF) steroids. The concentrations of the CSF steroids are pronouncedly lower in comparison with the ones in circulation. The available data indicate that the levels of pregnenolone sulfate substantially increase in the rat brain tissue after the administration of pregnenolone into the circulation. In the human circulation there are about two orders of magnitude higher levels of pregnenolone sulfate compared to the free pregnenolone. Our data show insignificant correlation between CSF and serum pregnenolone, but a borderline one between CSF pregnenolone and serum pregnenolone sulfate. Therefore in humans, the circulating pregnenolone sulfate might be of an importance for pregnenolone concentration in the CNS. In contrast to free pregnenolone, dehydroepiandrosterone (DHEA) in the CSF correlates with both unconjugated and conjugated DHEA in the serum. These data as well as the low C17-hydroxylase-C17,20-lyase activity in the CNS might indicate that DHEA levels in the CNS are influenced by peripheral levels of DHEA and its sulfate. According to the information, available part of the neurosteroids may be synthesized de novo in the CNS, but substantial part of the steroid metabolites may be also synthesized in the CNS from the steroid precursors or directly transported through BBB from the periphery. The processes mentioned above may be complimentary in some cases. Brain synthesis may provide minimal level of neurosteroids, which are indispensable for the CNS functions. Thus, brain steroids of peripheral origin may reflect various physiological situations or even pathologies. This article is part of a Special Issue entitled: Neuroactive Steroids: Focus on Human Brain.

Effect of chronic hCG administration on Alzheimer's-related cognition and A beta accumulation in PS1KI mice

Age-associated changes in the reproductive hormones-the gonadal steroid hormones and the gonadotropins-have been identified as potential risk factors for Alzheimer's disease (AD). However, levels of gonadotropins and estrogens are closely linked in vivo, and it has proven difficult to separate the effects of gonadotropins from the well-documented estrogenic effects on AD-related neuropathology in experimental models of menopause. To assess the effects of gonadotropins on cognition and AD biochemical markers independent of estrogenic effects, a potent analog of luteinizing hormone [human chorionic gonadotropin (hCG)] was administered to ovariectomized presenilin1 knock-in mice (PS1KI). Gonadotropin administration was found to induce hyperactivity and anxiety (Open Field Maze and Taste Neophobia Task) and working memory dysfunction, without altering reference memory (Morris Water Maze). Although gonadotropin administration modestly altered β amyloid (Aβ40) levels, levels of the longer more toxic form (Aβ42) were unaffected. Furthermore, altered Aβ40 levels were not associated with observed behavioral and cognitive impairments. These findings provide proof, in principle, that the gonadotropin hormones play a role in the modulation of AD-related behavior, cognition, and neuropathology.

Peripheral neuroactive steroids may be as good as the steroids in the cerebrospinal fluid for the diagnostics of CNS disturbances

To compare the predictivity of the neuroactive steroids in the cerebrospinal fluid and peripheral blood for the diagnostics of CNS disturbances, eighteen unconjugated steroids were quantified in the cerebrospinal fluid (CSF) from the 3rd ventricle and 18 unconjugated steroids and 7 steroid polar conjugates were measured in the serum using GC-MS and RIA. Eight postmenopausal women (56-78 years of age) and 7 men (22-88 years of age) with hydrocephalus were enrolled in the study. The sensitivity of the method ranged from low femtogram to low picogram levels depending on the steroid fragmentation pattern. Using multivariate regression, a model for simultaneous prediction of the CSF steroids from the serum steroids was completed. Then, the penetrability of the individual steroids across the blood-brain-barrier was evaluated and the sources of various brain steroids were estimated. Our data show that a part of the steroids may be synthesized de novo in the CNS. However, substantial part of the steroid metabolites may be synthesized in the CNS from the steroid precursors or directly transported from the periphery. The CNS in situ synthesis and transport from periphery might be complementary in some cases, i.e. brain synthesis might provide minimum level of steroids, which are indispensable for the CNS functions.

Effects of the LHRH antagonist Cetrorelix on the brain function in mice

The decapeptide Cetrorelix, an LHRH antagonist, inhibits gonadotropin and sex steroid secretion. Cetrorelix is used for IVF-ET procedures and for the treatment of patients with prostate carcinoma, benign prostatic hyperplasia, endometriosis, leiomyomas and, ovarian cancer. However little is known about the effects of Cetrorelix on the brain function. In the present work the influence of Cetrorelix on different aspects of the brain function was studied following its administration into the lateral brain ventricle in mice. The effects tested included the impairment of the consolidation of a passive avoidance reflex caused by beta-amyloid 25-35, anxiolytic action in the plus-maze, antidepressive action in a forced swimming test and a tail suspension test and open-field behavior. In the passive avoidance test, beta-amyloid 25-35 administered immediately after the learning trial impaired the consolidation of passive avoidance learning. Cetrorelix fully blocked the impairment of the consolidation of passive avoidance learning when given icv 30 min following beta-amyloid 25-35 administration. If beta-amyloid 25-35 and Cetrorelix icv were given simultaneously, the Cetrorelix attenuated, but did not block the action of the beta-amyloid 25-35. Cetrorelix elicited anxiolytic action in the plus-maze, depending on the dose used. In the forced swimming and tail suspension tests, Cetrorelix demonstrated antidepressive-like action. Concerning open-field behavior, Cetrorelix displayed no action on locomotion, rearing or grooming. The results demonstrate that Cetrorelix affects brain function: and is able to correct the impairment of the memory consolidation caused by beta-amyloid 25-35. Cetrorelix also elicits anxiolytic and antidepressive action, but it does not influence the open-field activity. Further experimental work with Cetrorelix is necessary, but the results imply the possible merit of a clinical trial with Cetrorelix in patients with anxiety, depression and Alzheimer's disease.

Anti-aggregation and fibril-destabilizing effects of sex hormones on alpha-synuclein fibrils in vitro

The alpha-synuclein aggregation in the brain is the hallmark of Lewy body diseases, including Parkinson's disease and dementia with Lewy bodies, and multiple system atrophy. Some epidemiological studies have revealed that estrogen therapy reduces the risk of Parkinson's disease in females. We examined the effects of estriol, estradiol, estrone, androstenedione, and testosterone on the formation and destabilization of alpha-synuclein fibrils at pH 7.5 and 37 degrees C in vitro, using fluorescence spectroscopy with thioflavin S and electron microscopy. These sex hormones, especially estriol, significantly exert anti-aggregation and fibril-destabilizing effects; and hence, could be valuable preventive and therapeutic agents for alpha-synucleinopathies.

Estrogen has anti-amyloidogenic effects on Alzheimer's beta-amyloid fibrils in vitro

Inhibition of the assembly of amyloid beta-peptide (Abeta) as well as the destabilization of preformed beta-amyloid fibrils (fAbeta) in the central nervous system could be valuable therapeutics of patients with Alzheimer's disease (AD). Epidemiological studies have indicated that estrogen therapy reduced the risk of developing AD in women. Here, we examined the effects of estrogen (estrone (E1), estradiol (E2), and estriol (E3)) and related sexual steroids (androstenedione (AND) and testosterone (TES)) on the polymerization, extension and destabilization of fAbeta(1-42) and fAbeta(1-40) at pH 7.5 at 37 degrees C in vitro, using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies. E1, E2, and E3 dose-dependently inhibited the formation, as well as destabilization of fAbetas. The overall anti-amyloidogenic activity of these molecules was in the order of: E3>E2=E1>>AND=TES. Estrogen could be a potential therapeutic agent to prevent or delay AD progression.

Gonadotropins: potential targets for preventive and therapeutic interventions in Alzheimer’s disease

Increased prevalence of Alzheimer’s disease (AD) in women has led to an interest in the role of hormonal changes in the neurodegenerative process. In particular, research has been directed towards investigating the effect of changes in sex hormone levels following reproductive senescence. Clinical trials of hormone-replacement therapy for the prevention of AD are proving contentious, and considerably more research is necessary before the benefit of the hormone replacement strategy can be ascertained. However, evidence is now emerging to support the notion that increased gonadotropin levels may confer an increased risk of AD. Gonadotropins have been implicated in the metabolism of β-amyloid, a key protein that is central to the pathogenesis of AD. Gonadotropin reduction represents a promising new target for therapeutic intervention in AD and, potentially, dementia in general. In this review, the authors discuss the therapeutic and preventive potential of gonadotropin-reducing agents in the management of AD.

Changes with aging of steroidal levels in the cerebrospinal fluid of women

OBJECTIVE

Age-related changes of steroid levels in the central nervous system (CNS) are not well understood. To investigate whether steroidal conditions in the CNS of women change with aging and menopause, steroid levels have been measured in serum and cerebrospinal fluid (CSF), and examined correlations with aging.

METHODS

Serum and CSF concentrations of estradiol (E2), cortisol, dehydroepiandrosterone (DHEA), DHEA sulfate (DHEAS) and albumin were measured in 80 female patients who underwent operations for benign gynecological diseases. They had no endocrinological or neurological disorders and were aged 17-71 years; 62 patients were in premenopause and 18 were in postmenopause.

RESULTS

Serum levels of E2 decreased markedly after menopause, while levels of DHEA and DHEAS decreased gradually with age. There was no significant change with age of serum cortisol levels. The CSF concentrations of E2 (0.2-3 pg/ml) decreased with age [correlation coefficient (r)= 0.31, P < 0.01]. The CSF DHEA levels (0.1-0.8 ng/ml) did not change with age although not significantly, but CSF cortisol levels (0.1-0.6 microg/dl) increased with age (r = 0.35, P < 0.01). The CSF DHEAS concentrations were below the sensitivity of the radioimmunoassay (RIA) (1 ng/ml). The CSF/serum ratios of cortisol increased with age (r = 0.30, P < 0.01), as did those of DHEA (r = 0.55, P < 0.01). Although serum albumin levels did not change throughout life, CSF albumin levels and CSF/serum albumin ratios increased gradually with age (r = 0.28, P = 0.052; r = 0.23, P = 0.114, respectively), but there was no significance. There were marked decreases of serum E2 and DHEA levels and CSF E2 levels in postmenopausal women (P < 0.05), but CSF cortisol levels increased (P < 0.05) and DHEA levels in CSF were maintained after menopause.

CONCLUSION

These results indicate that steroids in CSF become cortisol dominated and deficient in estrogens with aging, especially after menopause.