Narrative reviewindependent cross-checkabstract only checked I-INTA-07 standard review
Which hormones make cows produce milk?
Endocrinology of milk production.
Overview
Svennersten-Sjaunja K et al.. Domestic animal endocrinology 2005 · PMID 15876512 · DOI 10.1016/j.domaniend.2005.03.006
Pregnancy hormones, growth hormone and prolactin build and run milk production; oxytocin only releases the milk.
Does the study support the specific claim? No · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Endocrinology of milk production
- How was the study done?
Narrative review
- How many people, animals or samples were studied?
Not applicable
- What was actually found?
Milk synthesis and milk ejection are regulated separately
- How large was the observed effect?
Not applicable
- What do the results mean in everyday life?
Year-round milk supply is not explained by oxytocin
- What are the study's limitations?
Review
- What does it say about Elawady's specific claim?
Contradicts the mechanism claimed
- Do the results apply to Germany and Europe?
High
- What can explicitly not be concluded from this study?
Farm practices in Egypt
Scientific in-depth review
1. Full reference
- Authors
- Svennersten-Sjaunja K et al.
- Journal
- Domestic animal endocrinology
- Year
- 2005
- Identifier
- PMID 15876512 DOI 10.1016/j.domaniend.2005.03.006
- Verification
- verified – PubMed efetch 2026-10-25
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
Endocrine regulation of milk production in dairy cows
3. Study design and population
- Study design
- Narrative review – Narrative review of lactation endocrinology
- Population
Dairy cows
- Country
Not applicable
- Period
Not applicable
- Sample size
Not applicable
- Inclusion and exclusion criteria
Not applicable
4. Methods and endpoints
- Exposure / intervention
Hormones of pregnancy and lactation
- Comparator
Not applicable
- Endpoints
Mammary development, milk synthesis, milk ejection
- Statistical methods
Not applicable
5. Actual results
- Results
Mammary growth is stimulated by growth hormone, prolactin, adrenocortical steroids, oestrogens and progesterone during pregnancy; local mechanisms in the gland regulate initiation and maintenance of lactation; oxytocin contracts myoepithelial cells for milk ejection.
- Absolute risks
Not applicable
- Authors' conclusion
Lactation involves coordinated endocrine, metabolic and local regulation.
6. Strengths
- Overview of lactation physiology
7. Weaknesses
- Narrative review
- Abstract only
8. Risk of bias
- Orienting tool
- none applicable
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- not assessable
- Rationale
Narrative review.
9. Assessment of the statistical interpretation
Not applicable.
10. Relevance to the specific claim
Shows that lactation is initiated by pregnancy and calving and maintained by several hormones and local factors; oxytocin is the let-down hormone.
11. Independent contrary findings
None.
12. Transferability to Germany and Europe
High.
13. Overall methodological judgement
Background physiology contradicting 'oxytocin keeps cows lactating all year'.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | not assessable |
| Precision of results | not applicable |
| Directness | direct |
| Reproducibility | replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
None.
15. Linked fact checks
- Cows naturally lactate seasonally (after giving birth), but dairy cows are injected with oxytocin all year round so that they keep producing milk; such milk is 'induced, not real'. – Studies contradicting or limiting the claim