Demographic, sampling- and assay-related confounders of endogenous oxytocin concentrations: A systematic review and meta-analysis.

Engel S, Laufer S, Miller R, Niemeyer H, Knaevelsrud C, Schumacher S

Frontiers in neuroendocrinology25 Jul 2019Cited by 42 (Europe PMC)

PMID31351080DOI10.1016/j.yfrne.2019.100775PepBankPUB-31351080

Publisher page PubMedAsk about this study

Summary

The text of this summary is not shown here, because the article license does not allow reuse. Read it at the source (opens in a new tab)

Text rights: Publisher copyright. Results still quote short attributed sentences.

Results from this study10

No result from this study comes from a test of the peptide.

Natural levels measured10

These results measure the body's own peptide. Nobody was given the peptide. They are not evidence about taking it. They are left out of key results, evidence counts and charts.

01HumanEndogenous levelSystematic reviewOther
In a meta-regression, measured oxytocin concentrations differed by specimen and extraction, and were extremely high in unextracted blood compared with extracted blood and other specimens.
In plain wordsMeasured levels of the body's own oxytocin were extremely high in unextracted blood compared with extracted blood and other samples.
Peptide
Oxytocin
Outcome
MixedOxytocin measurement by specimen and extraction
Study
n = 12,741
Outcome group
Endogenous peptide levels · Endocrine and hormones
Source sentences
Summary
Predicted oxytocin concentrations differed depending on specimen and extraction: Measurements were extremely high in unextracted blood, compared to extracted blood and other specimens.
1 context sentence(design, population, supporting numbers)
Summary · context
We performed meta-regressions on k = 229 studies (n = 12 741 participants), testing whether specimen, extraction, sex, age, time of day, or fasting instructions influenced oxytocin measurements.
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Report a problemFND-3135108001
02HumanEndogenous levelSystematic reviewOther
In a meta-regression, measured oxytocin concentrations were higher in samples with more female participants.
In plain wordsMeasured levels of the body's own oxytocin were higher in samples with more women.
Peptide
Oxytocin
Outcome
IncreaseOxytocin concentration by sex
Study
n = 12,741
Outcome group
Endogenous peptide levels · Endocrine and hormones
Source sentences
Summary
Measurements were higher in samples with more female participants
1 context sentence(design, population, supporting numbers)
Summary · context
We performed meta-regressions on k = 229 studies (n = 12 741 participants), testing whether specimen, extraction, sex, age, time of day, or fasting instructions influenced oxytocin measurements.
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Report a problemFND-3135108002
03HumanEndogenous levelSystematic reviewOther
In a meta-regression, measured oxytocin concentrations were higher in samples with higher age.
In plain wordsMeasured levels of the body's own oxytocin were higher in samples from older people.
Peptide
Oxytocin
Outcome
IncreaseOxytocin concentration by age
Study
n = 12,741
Outcome group
Endogenous peptide levels · Endocrine and hormones
Source sentences
Summary
Measurements were higher in samples with more female participants and higher age.
1 context sentence(design, population, supporting numbers)
Summary · context
We performed meta-regressions on k = 229 studies (n = 12 741 participants), testing whether specimen, extraction, sex, age, time of day, or fasting instructions influenced oxytocin measurements.
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Report a problemFND-3135108003
04HumanEndogenous levelSystematic reviewOther
In a meta-regression, oxytocin concentrations increased from morning to afternoon.
In plain wordsMeasured levels of the body's own oxytocin rose from morning to afternoon.
Peptide
Oxytocin
Outcome
IncreaseOxytocin concentration, morning vs afternoon
Study
n = 12,741
Outcome group
Endogenous peptide levels · Endocrine and hormones
Source sentences
Summary
Oxytocin concentrations increased from morning to afternoon.
1 context sentence(design, population, supporting numbers)
Summary · context
We performed meta-regressions on k = 229 studies (n = 12 741 participants), testing whether specimen, extraction, sex, age, time of day, or fasting instructions influenced oxytocin measurements.
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Report a problemFND-3135108010
05HumanEndogenous levelSystematic reviewOther
In a meta-regression, instructions not to smoke before sampling were correlated with higher oxytocin in unextracted samples.
In plain wordsInstructions not to smoke before sampling were linked to higher measured levels of the body's own oxytocin in unextracted samples.
Peptide
Oxytocin
Outcome
IncreaseOxytocin concentration, no-smoking instruction in unextracted samples
Study
n: not reported in source
Outcome group
Endogenous peptide levels · Endocrine and hormones
Source sentences
Summary
Instructions not to smoke before sampling were correlated with higher oxytocin in unextracted samples.
1 context sentence(design, population, supporting numbers)
Summary · context
We performed meta-regressions on k = 229 studies (n = 12 741 participants), testing whether specimen, extraction, sex, age, time of day, or fasting instructions influenced oxytocin measurements.
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Report a problemFND-3135108004
06HumanEndogenous levelSystematic reviewOther
In a meta-regression, instructions to refrain from eating had no impact on measured oxytocin concentrations.
In plain wordsInstructions to refrain from eating made no difference to measured levels of the body's own oxytocin.
Peptide
Oxytocin
Outcome
No significant changeOxytocin concentration, instruction to refrain from eating
Study
n: not reported in source
Outcome group
Endogenous peptide levels · Endocrine and hormones
Source sentences
Summary
There was no impact of instructions to refrain from eating, drinking, consume caffeine, alcohol or exercising.
1 context sentence(design, population, supporting numbers)
Summary · context
We performed meta-regressions on k = 229 studies (n = 12 741 participants), testing whether specimen, extraction, sex, age, time of day, or fasting instructions influenced oxytocin measurements.
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Report a problemFND-3135108005
07HumanEndogenous levelSystematic reviewOther
In a meta-regression, instructions to refrain from drinking had no impact on measured oxytocin concentrations.
In plain wordsInstructions to refrain from drinking made no difference to measured levels of the body's own oxytocin.
Peptide
Oxytocin
Outcome
No significant changeOxytocin concentration, instruction to refrain from drinking
Study
n: not reported in source
Outcome group
Endogenous peptide levels · Endocrine and hormones
Source sentences
Summary
There was no impact of instructions to refrain from eating, drinking, consume caffeine, alcohol or exercising.
1 context sentence(design, population, supporting numbers)
Summary · context
We performed meta-regressions on k = 229 studies (n = 12 741 participants), testing whether specimen, extraction, sex, age, time of day, or fasting instructions influenced oxytocin measurements.
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Report a problemFND-3135108006
08HumanEndogenous levelSystematic reviewOther
In a meta-regression, instructions to refrain from caffeine had no impact on measured oxytocin concentrations.
In plain wordsInstructions to avoid caffeine made no difference to measured levels of the body's own oxytocin.
Peptide
Oxytocin
Outcome
No significant changeOxytocin concentration, instruction to refrain from caffeine
Study
n: not reported in source
Outcome group
Endogenous peptide levels · Endocrine and hormones
Source sentences
Summary
There was no impact of instructions to refrain from eating, drinking, consume caffeine, alcohol or exercising.
1 context sentence(design, population, supporting numbers)
Summary · context
We performed meta-regressions on k = 229 studies (n = 12 741 participants), testing whether specimen, extraction, sex, age, time of day, or fasting instructions influenced oxytocin measurements.
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Report a problemFND-3135108007
09HumanEndogenous levelSystematic reviewOther
In a meta-regression, instructions to refrain from alcohol had no impact on measured oxytocin concentrations.
In plain wordsInstructions to avoid alcohol made no difference to measured levels of the body's own oxytocin.
Peptide
Oxytocin
Outcome
No significant changeOxytocin concentration, instruction to refrain from alcohol
Study
n: not reported in source
Outcome group
Endogenous peptide levels · Endocrine and hormones
Source sentences
Summary
There was no impact of instructions to refrain from eating, drinking, consume caffeine, alcohol or exercising.
1 context sentence(design, population, supporting numbers)
Summary · context
We performed meta-regressions on k = 229 studies (n = 12 741 participants), testing whether specimen, extraction, sex, age, time of day, or fasting instructions influenced oxytocin measurements.
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Report a problemFND-3135108008
10HumanEndogenous levelSystematic reviewOther
In a meta-regression, instructions to refrain from exercising had no impact on measured oxytocin concentrations.
In plain wordsInstructions to avoid exercise made no difference to measured levels of the body's own oxytocin.
Peptide
Oxytocin
Outcome
No significant changeOxytocin concentration, instruction to refrain from exercising
Study
n: not reported in source
Outcome group
Endogenous peptide levels · Endocrine and hormones
Source sentences
Summary
There was no impact of instructions to refrain from eating, drinking, consume caffeine, alcohol or exercising.
1 context sentence(design, population, supporting numbers)
Summary · context
We performed meta-regressions on k = 229 studies (n = 12 741 participants), testing whether specimen, extraction, sex, age, time of day, or fasting instructions influenced oxytocin measurements.
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Report a problemFND-3135108009

AI wrote and checked these results. AI can make mistakes, so check important results against the source.

Version history

PepBank keeps every version of the data on this study. Status changes from Retraction Watch, Europe PMC and Crossref are listed with their source.

Version 2Current
9 Oct 2026, 18:17 UTC
Study results updated
Version 1
9 Oct 2026, 02:48 UTC
First added · source update from Europe PMC

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