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Allopregnanolone is a neurosteroid with significant implications for hormone, brain and mood health.  

The importance of allopregnanolone lies in its wide-ranging effects on the nervous system, hormonal balance, and mental health. Its levels fluctuate in response to different physiological conditions and can indicate various health states or disease progressions.

This article explores the biochemical nature of allopregnanolone, its functions in the human body, and its potential as a biomarker to provide greater understanding of the connections between hormone, mental and cognitive health. 

What is Allopregnanolone?

Allopregnanolone, often abbreviated as ALLO, is a neurosteroid synthesized in the brain and other parts of the body.  It is a metabolite of progesterone that, along with allopregnanediol, is chemically classified as a pregnane steroid. 

ALLO is made in the brain and peripheral tissues,including the adrenal glands, ovaries, and testes. The conversion of progesterone to allopregnanolone begins when progesterone is converted to 5α-dihydroprogesterone (5α-DHP) by the enzyme 5α-reductase. Then 5α-DHP is further converted to allopregnanolone by the enzyme 3α-hydroxysteroid-dehydrogenase (3α-HSD).  [8.]

ALLO plays a critical role in the modulation of several physiological processes, owing to its ability to act on the brain's GABA-A receptors.

ALLO plays a crucial role in brain development, adolescent and adult behavior, and nervous system maturation, with levels fluctuating throughout development and pregnancy. 

Furthermore, ALLO levels in the nervous system are influenced by neurodegenerative and psychiatric disorders, which exhibit sex-dimorphic features, highlighting the complex interplay between ALLO and neurological health.  [3.]

Allopregnanolone is known for its potent neuroprotective, anxiolytic, and possibly antidepressant properties. It works by enhancing the effects of GABA, the primary inhibitory neurotransmitter in the brain, leading to a calming, sedative effect that manifests anxiolytic and stress-reducing effects.  [3.]

The levels of allopregnanolone can vary significantly based on several factors such as age, sex, hormonal changes, and overall health status. It is particularly noted for its fluctuations during the menstrual cycle, pregnancy, and menopause in women, indicating its close relationship with reproductive health and hormonal balance. 

Factors Influencing Production

The production of allopregnanolone is influenced by numerous factors. Hormonal fluctuations, particularly those related to the menstrual cycle, pregnancy, and menopause, play a significant role in its synthesis. 

Stress and emotional states can decrease its production, as can the presence of certain medical conditions.  [4.]

Moreover, lifestyle factors such as diet, exercise, and sleep patterns can indirectly affect allopregnanolone levels by altering the body's hormonal balance and metabolic functions.  [9., 13.]

How Long Does It Take to Make Allopregnanolone in the Body?

The timeframe for allopregnanolone production in the body varies depending on several factors, including the efficiency of the enzymatic conversion processes and the availability of precursors like progesterone. 

The body's ability to synthesize allopregnanolone can be relatively quick as it responds to immediate physiological signals such as changes in reproductive hormone levels. 

However, this rapid synthesis can also be influenced by longer-term factors like chronic health conditions or prolonged stress, which may alter the body's capacity to produce allopregnanolone consistently.  [1.]

The Biological Actions of Allopregnanolone

Neurological Effects

Allopregnanolone exerts a profound impact on the central nervous system. Its primary action is modulation of the GABA-A receptor with 10 times the potency of benzodiazepines.  [8.]

ALLO strongly enhances the inhibitory effects of GABA, which results in sedative, anxiolytic, and potentially antidepressant effects. This modulation is crucial in maintaining neural balance and preventing over-excitation, which can lead to neurological disorders. 

ALLO also demonstrates neuroprotective properties, offering potential therapeutic avenues for conditions like epilepsy, neuropathic pain, and even injuries and neurodegenerative diseases.  [5.]

Impact on Hormonal Balance and Reproductive Health [10.]

Allopregnanolone plays varying roles across a woman's reproductive lifespan, influencing neuroendocrine mechanisms during puberty, menstrual cycle fluctuations, peripartum periods, and menopause. 

In puberty ALLO levels increase gradually, potentially affecting synaptic pruning and neurosecretory functions. 

During the menstrual cycle, ALLO rises across the luteal phase alongside progesterone, correlating with mood changes, particularly in premenstrual dysphoric disorder (PMDD).  [7.]

In peripartum periods, ALLO levels rise steadily during pregnancy, but drop abruptly postpartum, potentially contributing to postpartum depression (PPD) through changes in receptor concentration.

Conversely, in menopausal transitions, evidence regarding ALLO levels is mixed, with studies suggesting both stable and decreased levels compared to fertile women, with potential implications for mood and hormonal therapy responses. 

These findings underscore the complex interplay between ALLO and reproductive hormonal fluctuations, impacting mood and psychiatric symptoms across different reproductive stages.

Allopregnanolone in Stress Response and Mental Health

Allopregnanolone's impact on stress response and mental health is a field of growing interest. By binding GABA-A receptors, ALLO regulates the body's response to stress, potentially mitigating the effects of chronic stress and anxiety.  

Its role in mental health is highlighted by recent research exploring its potential as a treatment for depression and anxiety disorders, particularly postpartum depression. Understanding the mechanisms through which Allopregnanolone influences mental health can open new therapeutic pathways for managing mental health conditions.

It may also stimulate dopamine release, which may play a role in ALLO’s mental health effects.  [10.]

Allopregnanolone is deficient in mood disorders, with significant changes in availability and function during pregnancy and postpartum periods. These changes include upregulation during pregnancy, peaking in the third trimester, followed by a rapid decline after childbirth. 

Dysregulation of allopregnanolone levels postpartum may contribute to postpartum depression, potentially due to abnormal neurosteroid enzyme expression and altered GABAA receptor function.  [11.]

Allopregnanolone has also been implicated in premenstrual dysphoric disorder (PMDD). Fluctuations in ALLO levels across the menstrual cycle may contribute to mood changes and symptoms of PMDD, potentially mediated through its action as a positive allosteric modulator of GABA-A receptors.  [7.]

Pharmacological treatments like finasteride and oral contraceptives, inhibiting allopregnanolone synthesis, can impact GABA-A receptor subunit expression, potentially leading to mood symptoms and other side effects. 

Laboratory Testing for Allopregnanolone

Indications for Testing

Testing for ALLO levels may be indicated when assessing certain neurological or hormonal conditions. 

These may include anxiety disorders, depression, premenstrual dysphoric disorder (PMDD), and other mood-related conditions. Additionally, it can be important in evaluating hormonal imbalances or fluctuations during different life stages such as pregnancy, menopause, or as part of fertility assessments.

Types of Tests Available

The measurement of allopregnanolone is typically done through blood, urine or saliva tests. 

The choice between blood, urine or saliva testing may depend on various factors including the specific clinical situation, the patient's comfort and convenience, and the healthcare provider's preference.

Interpretation of Test Results

Interpreting the results of Allopregnanolone testing requires an understanding of the normal range of levels, which can vary based on age, sex, and physiological state.  It's important to consult the ordering  lab company for their reference ranges used.

One lab company offering testing for ALLO reports a salivary reference range of < 15 pg/mL and urinary reference range of 2.23-14.87 μg/g Cr for premenopausal women in the luteal phase of their cycle, or people on supplemented progesterone.

Testing Biomarkers Related to Allopregnanolone

Hormones and Neurotransmitters Linked to Allopregnanolone

Understanding ALLO levels in the context of other related biomarkers may be desired for a comprehensive assessment. 

Hormones like progesterone, from which allopregnanolone is derived, should be considered. 

Clinicians may want to order ALLO levels as part of a broader assessment of gonadal, adrenal, and/or thyroid hormones, especially when trying to determine the root cause of pathology.  Additionally, neurotransmitter testing may be desired.  

Neurotransmitters such as GABA also have a close relationship with ALLO. Evaluating these related biomarkers can provide deeper insights into an individual's hormonal and neurological state, offering a more holistic understanding of their health.

Natural Ways to Support Healthy Progesterone and Allopregnanolone Levels: How Can I Increase Allopregnanolone Naturally?

Because ALLO is a metabolite of progesterone, supporting healthy progesterone levels will support ALLO.  Additionally, the proper metabolism of progesterone is essential for appropriate ALLO production.

Diet and lifestyle measures can have a profound impact on hormone health.  Individuals seeking additional insight and support should seek medical advice including testing and assessment from a licensed healthcare professional.

Balanced diet rich in whole foods: incorporate fruits, vegetables, whole grains, lean proteins, and healthy fats to provide essential nutrients and support hormonal balance.

Manage stress: practice stress-reducing techniques such as meditation, deep breathing exercises, yoga, or mindfulness to lower cortisol levels, promote sex hormone production, and facilitate progesterone’s conversion to ALLO.  [12.]

Maintain healthy body weight: aim for a healthy weight through regular exercise and balanced nutrition, as excess body fat can lead to hormonal imbalances.  [13.]

Adequate sleep: prioritize quality sleep to optimize hormone regulation and support overall well-being.  [9.]

Limit alcohol intake: excessive alcohol consumption can disrupt hormone levels, so moderate intake is recommended.  [6.]

Avoid exposure to endocrine disruptors: minimize exposure to environmental toxins, such as pesticides, plastics, and chemicals found in personal care products, which can interfere with hormone function.  [4.]

Herbs and botanicals: certain herbs like chasteberry (Vitex agnus-castus) may help support progesterone levels, although consultation with a healthcare professional is advised.  [2.]

Testing Options for ALLO

Click here to explore testing panels that contain ALLO and order ALLO testing.

Allopregnanolone is a naturally occurring hormone in your body. It's a type of neurosteroid, which means it's produced in the brain and plays a significant role in your nervous system's function. Allopregnanolone is derived from progesterone, a hormone that's crucial for both men and women, although it's often associated with pregnancy in women. One of the key roles of Allopregnanolone is to modulate the activity of GABA, a neurotransmitter in your brain. Neurotransmitters are like the body's communication system, sending signals between nerve cells. GABA is particularly important because it helps to reduce neuronal excitability, which means it helps to calm the brain and promote relaxation. Allopregnanolone is like a natural tranquilizer for your brain, helping to maintain a sense of calm and balance. It's a crucial part of your body's complex hormonal system, working behind the scenes to keep your brain functioning smoothly.
If Your Levels Are High
High levels of Allopregnanolone could indicate a variety of things as this hormone plays a significant role in our nervous system. Allopregnanolone is like our body's natural chill pill, helping to keep our brain calm and balanced. It does this by interacting with GABA, a neurotransmitter that helps to reduce overactivity in the brain. High levels of Allopregnanolone could be due to certain medications, such as benzodiazepines or barbiturates, which are known to increase the activity of GABA. It could also be due to hormonal changes, as Allopregnanolone is derived from progesterone, a hormone that fluctuates throughout the menstrual cycle and during pregnancy. Additionally, certain health conditions, such as premenstrual dysphoric disorder (PMDD) or postpartum depression, have been linked to changes in Allopregnanolone levels. However, it's important to remember that everyone's body is different, and what's considered a "high" level for one person might be normal for another.
Symptoms of High Levels
Symptoms of high levels of Allopregnanolone could potentially include feelings of sedation, drowsiness, or lethargy, given its role in promoting relaxation in the brain. However, it's also possible that high levels of Allopregnanolone might not cause any noticeable symptoms at all.
If Your Levels are Low
Low levels of Allopregnanolone could mean that your body's natural calming system isn't working as well as it should be. Allopregnanolone is a hormone made in your brain that helps keep things calm and balanced. It does this by working with a brain chemical called GABA, which sends signals between nerve cells to help reduce overactivity and promote relaxation. If you don't have enough Allopregnanolone, your brain might not be able to keep things as calm and balanced as it should. This could be due to a variety of reasons, such as stress, certain medications like benzodiazepines or steroids, or conditions like premenstrual syndrome (PMS), postpartum depression, or certain types of epilepsy.
Symptoms of Low Levels
Symptoms of low levels of Allopregnanolone could include increased anxiety, mood swings, difficulty sleeping, and heightened sensitivity to stress.
See References

[1.] Bali A, Jaggi AS. Multifunctional aspects of allopregnanolone in stress and related disorders. Prog Neuropsychopharmacol Biol Psychiatry. 2014 Jan 3;48:64-78. doi: 10.1016/j.pnpbp.2013.09.005. Epub 2013 Sep 14. PMID: 24044974.

[2.] Bokelmann JM. Chasteberry/Chaste Tree/Vitex (Vitex agnus castus). Medicinal Herbs in Primary Care. Published online 2022:279-287. doi: 

[3.] Diviccaro S, Cioffi L, Falvo E, Giatti S, Melcangi RC. Allopregnanolone: An overview on its synthesis and effects. J Neuroendocrinol. 2022 Feb;34(2):e12996. doi: 10.1111/jne.12996. Epub 2021 Jun 29. PMID: 34189791; PMCID: PMC9285581. 

[4.] Fowler PA, Bellingham M, Sinclair KD, et al. Impact of endocrine-disrupting compounds (EDCs) on female reproductive health. Molecular and Cellular Endocrinology. 2012;355(2):231-239. doi:

[5.] Guennoun R, Labombarda F, Gonzalez Deniselle MC, Liere P, De Nicola AF, Schumacher M. Progesterone and allopregnanolone in the central nervous system: Response to injury and implication for neuroprotection. The Journal of Steroid Biochemistry and Molecular Biology. 2015;146:48-61. doi: 

[6.] Hakim RB, Gray RH, Zacur H. Alcohol and caffeine consumption and decreased fertility. Fertil Steril. 1998 Oct;70(4):632-7. doi: 10.1016/s0015-0282(98)00257-x. Erratum in: Fertil Steril 1999 May;71(5):974. PMID: 9797089. 

[7.] Hantsoo L, Epperson CN. Allopregnanolone in premenstrual dysphoric disorder (PMDD): Evidence for dysregulated sensitivity to GABA-A receptor modulating neuroactive steroids across the menstrual cycle. Neurobiol Stress. 2020 Feb 4;12:100213. doi: 10.1016/j.ynstr.2020.100213. PMID: 32435664; PMCID: PMC7231988.

[8.] Kimball A, Dichtel LE, Nyer MB, Mischoulon D, Fisher LB, Cusin C, Dording CM, Trinh NH, Yeung A, Haines MS, Sung JC, Pinna G, Rasmusson AM, Carpenter LL, Fava M, Klibanski A, Miller KK. The allopregnanolone to progesterone ratio across the menstrual cycle and in menopause. Psychoneuroendocrinology. 2020 Feb;112:104512. doi: 10.1016/j.psyneuen.2019.104512. Epub 2019 Nov 14. PMID: 31780185; PMCID: PMC6935417. 

[9.] Lateef OM, Akintubosun MO. Sleep and Reproductive Health. J Circadian Rhythms. 2020 Mar 23;18:1. doi: 10.5334/jcr.190. PMID: 32256630; PMCID: PMC7101004. 

[10.] McEvoy K, Osborne LM. Allopregnanolone and reproductive psychiatry: an overview. Int Rev Psychiatry. 2019 May;31(3):237-244. doi: 10.1080/09540261.2018.1553775. Epub 2019 Jan 31. PMID: 30701996; PMCID: PMC6594874. 

[11.] Pinna G. Allopregnanolone, the Neuromodulator Turned Therapeutic Agent: Thank You, Next? Front Endocrinol (Lausanne). 2020 May 14;11:236. doi: 10.3389/fendo.2020.00236. Erratum in: Front Endocrinol (Lausanne). 2020 Jul 30;11:507. PMID: 32477260; PMCID: PMC7240001.

[12.] Ranabir S, Reetu K. Stress and hormones. Indian J Endocrinol Metab. 2011 Jan;15(1):18-22. doi: 10.4103/2230-8210.77573. PMID: 21584161; PMCID: PMC3079864. 

[13.] Zheng L, Yang L, Guo Z, Yao N, Zhang S, Pu P. Obesity and its impact on female reproductive health: unraveling the connections. Front Endocrinol (Lausanne). 2024 Jan 9;14:1326546. doi: 10.3389/fendo.2023.1326546. PMID: 38264286; PMCID: PMC10803652.

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