Pharmacokinetics of progesterone and its metabolites allopregnanolone and pregnanolone after oral administration of low-dose progesterone

Advances in progesterone delivery systems: Still work in progress?

Progesterone is a natural steroidal sex hormone in the human body, mainly secreted through the adrenal cortex, ovary, and placenta. In humans, progesterone is essential for endometrium transformation in the uterus at the time of ovulation and maintenance of pregnancy. When the body cannot produce enough progesterone for specific ailments, it is administered via different routes such as oral, vaginal, transdermal, topical, parental, and intranasal routes. Although progesterone is commercially available in multiple conventional formulations, low solubility, less permeability and extensive hepatic first-pass metabolism are the major constraints to its delivery. These challenges can be overcome substantially by formulating progesterone into novel delivery systems like lipid carriers, polymeric carriers, hydrogels, several nanocarriers, depot and controlled release systems. Various research papers and patents have been published in the last two decades on progesterone delivery systems; clinical studies were conducted to establish safety and efficacy. This review is focused on the pharmacodynamic and pharmacokinetic parameters of progesterone, its delivery constraints, and various advanced delivery systems of progesterone.

Effects of acute estradiol and progesterone on perimenstrual exacerbation of suicidal ideation and related symptoms: a crossover randomized controlled trial

Female suicide attempts peak peri-menstrually-around the onset of menses-when the ovarian steroids estradiol (E2) and progesterone (P4) fall rapidly. Given preclinical evidence that withdrawal from either E2 or P4 can provoke behaviors consistent with elevated suicide risk, we hypothesized that withdrawal from one or both of these steroids contributes to perimenstrual exacerbation of suicidal ideation (SI) and related symptoms. In a randomized, controlled, double-blind crossover experiment (NCT03720847), a transdiagnostic sample of naturally cycling, medically healthy psychiatric outpatients reporting past-month SI completed two conditions during two different 14-day experimental intervals (days 7-20 where the luteinizing hormone surge = day 0), separated by a monthlong washout cycle. In the E2 and P4 (EP) condition, participants received transdermal E2 (0.1 mg/day) plus oral micronized P4 (200 mg/day as 100 mg twice daily) to buffer perimenstrual steroid withdrawal. A matched placebo (PBO) condition allowed natural perimenstrual steroid withdrawal. Participants reported daily SI and planning (primary outcomes) and indices of depression (low mood, hopelessness), threat sensitivity (anxiety, perceived stress), executive functioning (difficulty concentrating, impulsivity), and social cognitive bias (rejection sensitivity, perceived burdensomeness). In baseline cycles, no participant met prospective criteria for DSM-5 premenstrual dysphoric disorder, but 59% met all criteria except full follicular symptom remission, and 93% showed the highest SI in the perimenstrual phase. Of 29 randomized, 28 were analyzed (14 EP-PBO, 14 PBO-EP). Experimental administration of E2 and P4 (relative to PBO) reduced perimenstrual exacerbation of SI, suicide planning, depression, hopelessness, perceived stress, rejection sensitivity, and perceived burdensomeness, particularly in the perimenstrual (natural E2 and P4 withdrawal) days. Further, delayed withdrawal from experimental E2 and P4 (but not PBO) recapitulated SI, hopelessness, and rejection sensitivity. Acute perimenstrual withdrawal from ovarian steroids may play a causal role in perimenstrual worsening of depression and SI.

Effect of Human Cytochrome P450 2D6 Polymorphism on Progesterone Hydroxylation

BACKGROUND AND OBJECTIVES

Herein, hydroxylation activities at the 6β-position and 21-position of progesterone mediated by human cytochrome P450 (CYP) 2D6 and its variants and the effects of psychotropic drugs on these hydroxylation activities were compared to clarify whether CYP2D6 polymorphisms and psychotropic drugs impact neurosteroid levels in the brain.

METHODS

Progesterone was incubated with CYP2D6.1, CYP2D6.2 (Arg296Cys, Ser486Thr), CYP2D6.10 (Pro34Ser, Ser486Thr), and CYP2D6.39 (Ser486Thr) in the absence or presence of typical psychotropic drugs (fluvoxamine, fluoxetine, paroxetine, fluphenazine, and milnacipran) and endogenous steroids (testosterone and cortisol). Then, 6β- and 21-hydroxyprogesterone levels were determined by high-performance liquid chromatography.

RESULTS

Although the Michaelis-Menten constants (Km) for progesterone 6β- and 21-hydroxylation reactions mediated by the different CYP2D6 variants were similar, the maximal velocity (Vmax) values of the reactions mediated by CYP2D6.1 and CYP2D6.2 were the highest, followed by those mediated by CYP2D6.39 and CYP2D6.10. Thus, the of progesterone 6β- and/or 21-hydroxylation reactions mediated by CYP2D6.1 and CYP2D6.2 showed the highest Vmax/Km values, followed by the reactions mediated by CYP2D6.39. All investigated compounds inhibited progesterone 21-hydroxylation mediated by CYP2D6 variants at high concentrations. Interestingly, at low concentrations, fluoxetine increased progesterone 21-hydroxylation mediated by CYP2D6.1, but not that mediated by CYP2D6.2 or CYP2D6.10. In addition, the Km value for CYP2D6.2 was elevated in the presence of fluoxetine, whereas the value for CYP2D6.1 was unaltered; however, Vmax values of both CYP2D6.1 and CYP2D6.2 were increased. Paroxetine competitively inhibited CYP2D6.1- and CYP2D6.2-mediated progesterone 21-hydroxylation.

CONCLUSIONS

These results suggest that CYP2D6 polymorphism can affect the stimulation/inhibition of progesterone 21-hydroxylation.

Progesterone, reproduction, and psychiatric illness

Mood and anxiety disorders are vastly overrepresented in women, and one important contributor to these differences is the fluctuation in sex steroids in women during the reproductive years. Considerable evidence supports a role for abnormal sensitivity to these hormonal fluctuations for some women, who develop mood symptoms associated with reproductive transitions. This chapter presents evidence of the role of endogenous progesterone and its metabolites in such mood symptoms, and then goes on to cover the evidence concerning exogenous progesterone's effects on mood. Overall, the literature does not support an association between exogenous progesterone and negative mood in the general population, but does indicate that subset of women may be vulnerable to such effects. Research is lacking on women with psychiatric illness.

Progesterone loading as a strategy for treating postpartum depression

Postpartum depression (PPD) is a severe disorder that adversely impacts both mothers and infants. It is associated with significant morbidity and mortality and reported prevalence is 11.5% (Ko, Rockhill, Tong, Morrow, & Farr. (2017). MMWR Morbidity and Mortality Weekly Report, 66(6), 153-158). Although PPD's fundamental pathophysiology remains to be fully illuminated, the influence of changes in perinatal hormones such as allopregnanolone (an endogenous progesterone metabolite) are most promising avenues of research. Conventional treatments for PPD are aligned with treatment strategies for depressive disorders. Brexanolone is a small molecule, neuroactive steroid GABA_A receptor allosteric modulator consisting of synthetic allopregnanolone and a solubilizing agent. In early 2019, brexanolone received approval in the United States for the treatment of PPD. Brexanolone is only available through a restricted program and is costly. Animal models demonstrate that progesterone prevents depression-like behaviors. However, studies of progesterone's effects in women suffering from PPD are few and inconclusive. We hypothesize that orally dosed progesterone will increase concentrations of allopregnanolone in the central nervous system, which should relieve symptoms of PPD.

Comparison of steroid hormone hydroxylation mediated by cytochrome P450 3A subfamilies

Hydroxylation activity at the 6β-position of steroid hormones (testosterone, progesterone, and cortisol) by human cytochromes P450 (CYP) 3A4, polymorphic CYP3A5, and fetal CYP3A7 were compared to understand the catalytic properties of the major forms of human CYP3A subfamily. Testosterone, progesterone, and cortisol 6β-hydroxylation activities of recombinant CYP3A4, CYP3A5, and CYP3A7 were determined by liquid chromatography. Michaelis constants (K_m) for CYP3A7-mediated 6β-hydroxylation of testosterone, progesterone, and cortisol were similar to those of CYP3A4 and CYP3A5. The maximal velocity (k_cat) and k_cat/K_m values for CYP3A4 were the highest, followed by CYP3A5 and those for CYP3A7 were the lowest among three CYP3A subfamily members. A decrease in K_m values for progesterone 6β-hydroxylation by CYP3A4, CYP3A5, and CYP3A7 in the presence of testosterone was observed, and the k_cat values for CYP3A5 gradually increased with increasing testosterone. This indicated that testosterone stimulated progesterone 6β-hydroxylation by all three CYP3A subfamily members. However, progesterone inhibited testosterone 6β-hydroxylation mediated by CYP3A4, CYP3A5, and CYP3A7. In conclusion, the k_cat values, rather than K_m values, for 6β-hydroxylation of three steroid hormones mediated by CYP3A7 were different from those for CYP3A4 and CYP3A5. In addition, the inhibitory/stimulatory pattern of steroid-steroid interactions would be different among CYP3A subfamily members.

Neuroendocrine Regulation of Anxiety: Beyond the Hypothalamic-Pituitary-Adrenal Axis

The central nervous system regulates and responds to endocrine signals, and this reciprocal relationship determines emotional processing and behavioural anxiety. Although the hypothalamic-pituitary-adrenal (HPA) axis remains the best-characterised system for this relationship, other steroid and peptide hormones are increasingly recognised for their effects on anxiety-like behaviour and reward. The present review examines recent developments related to the role of a number of different hormones in anxiety, including pregnane neurosteroids, gut peptides, neuropeptides and hormonal signals derived from fatty acids. Findings from both basic and clinical studies suggest that these alternative systems may complement or occlude stress-induced changes in anxiety and anxiety-like behaviour. By broadening the scope of mechanisms for depression and anxiety, it may be possible to develop novel strategies to attenuate stress-related psychiatric conditions. The targets for these potential therapies, as discussed in this review, encompass multiple circuits and systems, including those outside of the HPA axis.

GABAA Receptor-Modulating Steroids in Relation to Women's Behavioral Health

In certain women, increased negative mood relates to the progesterone metabolite, allopregnanolone (allo), during the luteal phase of ovulatory menstrual cycles, the premenstrual dysphoric disorder (PMDD). In anovulatory cycles, no symptom or sex steroid increase occurs but symptoms return during progesterone/allo treatment. Allo is a potent GABAA receptor-modulating steroid and as such is expected to be calming and anxiolytic. A relation to negative mood is unexpected. However, this paradoxical effect can be induced by all GABAA receptor modulators in low concentrations whereas higher concentrations are calming. The severity of the mood symptoms relate to allo in an inverted U-shaped curve at endogenous luteal-phase serum concentrations. Allo's effects on the GABAA receptor can be antagonized by isoallopregnanolone (ISO), an antagonist to allo. ISO has also been used in a preliminary clinical trial on PMDD ameliorating symptoms with good effect in PMDD patients.

Progesterone in Peri- and Postmenopause: A Review

Around 14.5 million peri- and postmenopausal women currently live in Germany. Moreover, approximately 450 000 women, each with a life expectancy of around 85 years, reach menopause every year in Germany. The challenge is therefore to find a therapy with few side effects which could improve the quality of life of women with menopausal symptoms. The aim of hormone therapy (HT) is to remedy hormone deficiencies using substances that offer the best trade-off between benefits and risks. This is where progesterone has a new and important role to play. Progesterone is one of the most important gestagens. Biologically effective progesterone formulations created with micronization techniques have been used in clinical practice since 1996. Nevertheless, up until 2003 preference was given to synthetic gestagens rather than progesterone. The increased breast cancer hazard ratio of 1.23 reported in the WHI study and of 2 given in the Million Women Study has been associated with the use of synthetic gestagens. In a comparison between synthetic gestagens and progesterone, the E3N Study showed that the transdermal administration of estrogen and progesterone did not lead to an increase in breast cancer rates (RR: 1.08). The administration of progesterone does not change the HDL/LDL cholesterol ratio. Because of its anti-mineralocorticoid effect, progesterone has no impact on carbohydrate metabolism, hemostasis, blood pressure, thrombogenicity and body weight. The administration of 200 mg/day progesterone over 12 days of a menstrual cycle or a daily administration of 100 mg combined with an estrogen are a safe and well-tolerated option to treat menopausal symptoms, with a better benefit risk profile compared to synthetic gestagens.

Progesterone effects on the discriminative stimulus, subjective and performance effects of triazolam in healthy, premenopausal women

There is accumulating evidence that sex plays a critical role in drug abuse. Female sex hormones have been shown to affect central nervous system function and modulate the effects of drugs of abuse. For example, γ-aminobutyric acid type A (GABA(A)) receptor function is positively modulated by progesterone metabolites. There is evidence from preclinical in-vitro and in-vivo studies as well as some clinical research suggesting that progesterone and its metabolites may enhance the behavioral effects of benzodiazepines, which also serve as positive modulators of GABA(A) receptors. The purpose of this experiment was to determine the independent and combined discriminative stimulus, subjective and psychomotor effects of progesterone and triazolam in healthy adult premenopausal women. Oral micronized progesterone (100 mg), triazolam (0.06, 0.12 and 0.25 mg/70 kg) and placebo were administered to healthy, premenopausal women (n=9) under conditions of low circulating sex hormones. Triazolam alone functioned as a discriminative stimulus and produced prototypical sedative-like effects (e.g., performance impairment, enhanced reports of sedative effects). Progesterone alone produced sedative-like effects on several subjective and performance measures, and the dose combination effects of progesterone and triazolam on several subjective measures of drug effect were similar to the summation of the two drug effects in isolation. Progesterone did not substitute for or modify the discriminative stimulus effects of triazolam. These results suggest that the parent hormone, progesterone, and triazolam have discordant neuropharmacological mechanisms of action. Additional research is necessary to determine the degree to which neurosteroids influence sex differences in benzodiazepine use and abuse.

Physiological doses of progesterone potentiate the effects of triazolam in healthy, premenopausal women

RATIONALE

Gender plays a critical role in the effects of drugs and drug abuse liability. Biological factors, including ovarian hormones, may contribute to gender differences in drug abuse. Preclinical and some clinical research suggests that progesterone and its metabolites have activity at the GABA(A) receptor and may enhance the effect of GABAergic compounds (e.g., benzodiazepines). Because women are exposed to varying levels of progesterone from puberty until menopause, and appear more sensitive to the negative consequences of benzodiazepine use, it is important to understand the impact of progesterone on GABAergic drug effects.

OBJECTIVES

The purpose of this experiment was to characterize the behavioral effects of progesterone, alone and in combination with the short-acting benzodiazepine, triazolam, to determine if progesterone potentiates the behavioral effects of triazolam.

METHODS

Oral micronized progesterone (0, 100, and 200 mg) and oral triazolam (0.00, 0.12, and 0.25 mg/70 kg) were administered to healthy, premenopausal women (n = 11) under conditions of low circulating sex hormones. The subjective, performance and physiological effects of progesterone, alone and in combination with triazolam, were assessed.

RESULTS

Triazolam alone produced prototypical sedative-like effects. Progesterone alone also engendered some sedative effects, although the time course of the effects was more limited than that of triazolam. Progesterone increased and extended the duration of triazolam effects and delayed the onset of triazolam peak effects, most notably at the 0.12 mg/70 kg dose.

CONCLUSIONS

Progesterone potentiates the behavioral effects of benzodiazepines and may contribute to benzodiazepine use and abuse among women.

Effects of acute progesterone administration upon responses to acute psychosocial stress in men

Animal studies suggest that neuroactive steroids, in particular progesterone and its metabolites, have stress-dampening effects. However, few studies have explored these effects in humans. In this study, we investigated the effects of acute progesterone administration on responses to the Trier Social Stress Test (TSST). Healthy men participated in the TSST 3.5 hrs after intramuscular injection of 0, 50, or 100 mg progesterone (N = 16, 14, and 14). We measured cardiovascular (heart rate, blood pressure), hormonal (plasma adrenocorticotrophic hormone, cortisol, and noradrenaline), and subjective (e.g., anxiety, arousal) responses to stress in the three groups. Before the TSST, progesterone injections increased plasma levels without altering physiological or subjective states. Stress produced its expected physiological and subjective effects among placebo-treated individuals. Progesterone 50 mg attenuated peak increases in plasma cortisol and reduced changes in negative mood and alertness after stress, yet it increased plasma noradrenaline and systolic blood pressure. Progesterone 100 mg also attenuated stress-induced increases in alertness and arousal, yet it potentiated stress-induced increases in diastolic pressure. Thus, progesterone dampened some of the psychological effects of stress but produced inconsistent effects on physiological stress responses.

Sex steroid induced negative mood may be explained by the paradoxical effect mediated by GABAA modulators

Certain women experience negative mood symptoms as a result of progesterone during the luteal phase of the menstrual cycle, progestagens in hormonal contraceptives, or the addition of progesterone or progestagens in sequential hormone therapy (HT). This phenomenon is believed to be mediated via the action of the progesterone metabolites on the GABA(A) system, which is the major inhibitory system in the mammalian CNS. The positive modulators of the GABA(A) receptor include allopregnanolone and pregnanolone, both neuroactive metabolites of progesterone, as well as benzodiazepines, barbiturates, and alcohol. Studies on the effect of GABA(A) receptor modulators have shown contradictory results; although human and animal studies have revealed beneficial properties such as anaesthesia, sedation, anticonvulsant effects, and anxiolytic effects, recent reports have also indicated adverse effects such as anxiety, irritability, and aggression. It has actually been suggested that several GABA(A) receptor modulators, including allopregnanolone, have biphasic effects, in that low concentrations increase an adverse, anxiogenic effect whereas higher concentrations decrease this effect and show beneficial, calming properties. The allopregnanolone increase during the luteal phase in fertile women, as well as during the addition of progesterone in HT, has been shown to induce adverse mood in women. The severity of these mood symptoms is related to the allopregnanolone serum concentrations in a manner similar to an inverted U-shaped curve. Negative mood symptoms occur when the serum concentration of allopregnanolone is similar to endogenous luteal phase levels, while low and high concentrations have less effect on mood. It has also been shown that progesterone/allopregnanolone treatment in women increases the activity in the amygdala (as measured with functional magnetic resonance imaging) in a similar way to the changes seen during anxiety reactions. However, it is evident that only certain women experience adverse mood during progesterone or GABA(A) receptor modulator treatments. Women with premenstrual dysphoric disorder (PMDD) have severe luteal phase related symptoms; in this phase, they show changes in GABA(A) receptor sensitivity and GABA concentrations that are related to the severity of the condition. These findings suggest that negative mood symptoms in women with PMDD are caused by the paradoxical effect of allopregnanolone mediated via the GABA(A) receptor.

CONCLUSION

Progesterone and progestagens induce negative mood, most probably via their GABA(A) receptor active metabolites. In postmenopausal women treated with progesterone and animals treated with allopregnanolone, there is a bimodal association between serum allopregnanolone concentration and adverse mood, resembling an inverted U-shaped curve. In humans, the maximal effective concentration of allopregnanolone for producing negative mood is within the range of physiological luteal phase serum concentrations.

Effects of bisphenol-A and other endocrine disruptors compared with abnormalities of schizophrenia: an endocrine-disruption theory of schizophrenia

In recent years, numerous substances have been identified as so-called "endocrine disruptors" because exposure to them results in disruption of normal endocrine function with possible adverse health outcomes. The pathologic and behavioral abnormalities attributed to exposure to endocrine disruptors like bisphenol-A (BPA) have been studied in animals. Mental conditions ranging from cognitive impairment to autism have been linked to BPA exposure by more than one investigation. Concurrent with these developments in BPA research, schizophrenia research has continued to find evidence of possible endocrine or neuroendocrine involvement in the disease. Sufficient information now exists for a comparison of the neurotoxicological and behavioral pathology associated with exposure to BPA and other endocrine disruptors to the abnormalities observed in schizophrenia. This review summarizes these findings and proposes a theory of endocrine disruption, like that observed from BPA exposure, as a pathway of schizophrenia pathogenesis. The review shows similarities exist between the effects of exposure to BPA and other related chemicals with schizophrenia. These similarities can be observed in 11 broad categories of abnormality: physical development, brain anatomy, cellular anatomy, hormone function, neurotransmitters and receptors, proteins and factors, processes and substances, immunology, sexual development, social behaviors or physiological responses, and other behaviors. Some of these similarities are sexually dimorphic and support theories that sexual dimorphisms may be important to schizophrenia pathogenesis. Research recommendations for further elaboration of the theory are proposed.

Effects of allopregnanolone on sedation in men, and in women on oral contraceptives

Allopregnanolone is a known GABA(A) receptor agonist not previously given to men, or to women using oral contraceptives (OC). The effects of metabolites of sex hormones on the GABA(A) receptor are different between men and women. OC are known to change GABA(A) receptor subunit composition. These factors might play a role in the differential effect of allopregnanolone in men and women, and in women with or without OC. To study the sedative effect of and sensitivity to allopregnanolone in men and in women with OC, nine healthy men (mean age 24.6 years) and nine healthy women on OC (mean age 21.8 years) were given three, increasing, intravenous dosages (0.015, 0.03, and 0.045 mg/kg) of allopregnanolone. Saccadic eye velocity (SEV), subjective ratings, and electroencephalography (EEG) were used to evaluate the response to allopregnanolone. Repeated blood samples for analyses of serum allopregnanolone levels were drawn throughout the study day. Allopregnanolone decreased SEV more in women than in men, and increased subjective ratings of 'sedation'. The results in women on OC are similar to earlier results in women without OC. Subjective ratings of 'contentedness' decreased in men but increased in women. Serum levels of allopregnanolone were more highly increased in men compared to women. Other pharmacokinetic parameters were not different between sexes. On the EEG, beta power increased in men. In conclusion, men and women on OC reacted differently to allopregnanolone.

Oral progesterone decreases saccadic eye velocity and increases sedation in women

The aim of this study was to investigate the neurophysiological and behavioural effects of a single dose of progesterone in women. Allopregnanolone is a metabolite of progesterone and a potent positive modulator of the GABA(A) receptor and produces sedative and anxiolytic effects. This study was designed to examine the effect of oral progesterone and the metabolite allopregnanolone in women. Women (n=15) in their follicular phase received oral progesterone (400mg) or placebo. Dependent measures included plasma levels of progesterone and allopregnanolone, saccadic eye velocity (SEV), subjective ratings (visual analogue scales), and reaction time. Administration of progesterone decreased SEV and increased sedation. This effect is probably due to enhanced GABA activity.

Allopregnanolone concentration and mood--a bimodal association in postmenopausal women treated with oral progesterone

RATIONALE

Allopregnanolone effects on mood in postmenopausal women are unclear thus far.

OBJECTIVES

Allopregnanolone is a neuroactive steroid with contradictory effects. Anaesthetic, sedative, and anxiolytic as well as aggressive and anxiogenic properties have been reported. The aim of this study is to compare severity of negative mood between women receiving different serum allopregnanolone concentrations during progesterone treatment.

MATERIALS AND METHODS

A randomized, placebo-controlled, double-blind, crossover study of postmenopausal women (n=43) treated with 2 mg estradiol daily during four treatment cycles. Oral micronized progesterone at 30, 60, and 200 mg/day, and placebo were added sequentially to each cycle. Participants kept daily symptom ratings using a validated rating scale. Blood samples for progesterone and allopregnanolone analyses were collected during each treatment cycle.

RESULTS

During progesterone treatment, women had significantly higher negative mood scores when allopregnanolone serum concentration was in the range of 1.5-2 nmol/l compared to lower and higher concentrations. In addition, women displayed a significant increase in negative mood during the progesterone treatment period, compared to the estradiol-only period when 30 mg progesterone daily was used. On the other hand, treatment with higher doses of progesterone had no influence on negative mood.

CONCLUSIONS

Mood effects during progesterone treatment seem to be related to allopregnanolone concentration, and a bimodal association between allopregnanolone and adverse mood is evident.