Non-Invasive Methods in Endocrinology Flashcards
(69 cards)
why use non-invasive methods?
Practicality
Animal welfare
Scientific validity
why use non-invasive methods? - Practicality
- broadly applicable (comparative perspective)
- only possibility for long-term studies in field
why use non-invasive methods? - Animal welfare
- avoids health risks and stress associated with capture/restraint
why use non-invasive methods? - Scientific validity
- allows studies in social context
- reduces effects of stress response on physiology (and behaviour)
Types of non-invasive methods
faeces
saliva
urine
hair/nail/feathers
water
milk
(… and others)
extraction methods
bioassays (e.g. enzyme immunoassays)
What does the suitability / choice of sample type depend on?
- feasibility of sample collection
- target hormone
- scientific question
what does choosing the ‘wrong’ sample type cause?
- costly
- time consuming
- lead to a mismatch of hormones and behaviour or masked hormone-behaviour relationships
Time lag between hormone secretion & appearances in matrices
1. saliva
2. urine
3. faecal
4. hair or wool
5. feathers
- saliva to study acute changes in hormone concentrations - changes within minutes of hormones being in blood
- urine samples take hours
- faecal samples take hours or days
- hair or wool samples - can quantify cumulative of the samples - days/weeks/months
- feathers - weeks/months - once the feather is fully grown no hormones get sent there
Choice between urine or faeces samples depends on?
- feasibility of sample collection - raining during urine sample, or urine sample in desert (may just soak into the ground)
- hormone of interest (e.g. peptide hormones only present in urine)
- species of interest - variation in the route of hormone excretion and metabolism
- storage/transport options
- research questions
(Christensen et al., 2022)
Urine or faeces for studying HPA activity?
Time lag of hormone secretion
differs between urine + faeces -> implications for their suitability for studying effects of different temporal nature on HPA-axis activity
(Christensen et al., 2022)
Urine or faeces for studying HPA activity?
what is lacking?
simultaneous comparisons of predictors of faecal and urinary GC metabolites (fGCs and uGCs) are lacking
(Christensen et al., 2022)
Urine or faeces for studying HPA activity?
what was investigated?
correlates of fGCs and uGCs in wild chacma baboons (Papio ursinus), including long-term (dominance rank, season, female reproductive state) and short-term (time of day, daily weather conditions) factors
(Christensen et al., 2022)
Urine or faeces for studying HPA activity?
results?
- correlated with increasing day length, fGCs gradually decreased from winter to summer
- no seasonal effect on uGCs but ‘rain days’ associated with increased uGCs
- pregnant females had significantly higher fGCs compared to cycling and lactating females; no effect of reproductive state on uGC
- Circadian effect for uGCs but not fGCs
(Christensen et al., 2022)
Urine or faeces for studying HPA activity?
1. what does the study highlight?
2. what uGCs offer?
3. where possible, what should be monitored? to obtain what?
4. shows importance of what?
- difference in inherent fluctuation between uGCs and fGCs and its potential consequences for HPA-axis activity monitoring
- uGCs offer the opportunity to study short-term effects but undergo more pronounced fluctuations, reducing their ability to capture long-term effects
- where possible, uGCs and fGCs should be monitored in tandem to obtain a comprehensive understanding of short- and long-term drivers of HPA-axis activity
- importance of choice of sampling
Factors Affecting Hormone Data Interpretation
- delayed excretion
- metabolic rate
- diurnal patterns
- effects of diet
- storage effects
- reproductive state
- sex
- disease
- season
- etc…
Delayed excretion (affecting hormone data interpretation)
urine vs faeces
faeces has delayed excretion (Wasser et al., 1998)
Delayed excretion (affecting hormone data interpretation)
Faecal cortisol metabolites in non-human primates: species and time lag (h)
1. Marmoset
2. Long-tail macaque
3. Barbary macaque
4. Baboon
5. Chimpanzee
6. Sifaka
7. Gibbon
- 8
- 28
- 46
- 36
- 26
- 26
- 27
(Goymann, 2012)
Metabolic rate (affecting hormone data interpretation)
high metabolic rate of bird = bigger faeces (more hormones)
hormone measurement on faecal samples depends on size of faeces
can effect sample measurements
(Sousa & Ziegler, 1998) (Smith & French, 1997)
Diurnal patterns (affecting hormone data interpretation)
urinary samples of Callithrix jacchus (Marmoset)
females:
- higher urinary cortisol at around 11:00 (highest peak during the day)
- lowest urinary cortisol at 18:00
males:
- higher urinary cortisol = 10:00/11:00
- lowest urinary cortisol = 13:00/15:00
(Higham et al., 2007)
effects of diet (affecting hormone data interpretation)
Olive baboons (Vitex doniana)
1. what have lab analyses show?
- show fruit contains more progesterone substances than leaves
fruit affects faecal progesterone (higher)
(Goymann, 2012)
Sex differences in hormone metabolism (affecting hormone data interpretation)
blood and faeces & droppings - male vs female
- males and females had equal hormone concentrations in their bloods
- males had a higher metabolic concentration than females in faeces & droppings
(Khan et al., 2002)
storage effects (affecting hormone data interpretation)
- best to freeze soon after collection
- samples split and stored at frozen (-20 degrees - lower faecal estrogen and glucocorticoids) or room temperature (higher faecal estrogen and glucocorticoids) - measured hormones concentrations at different times
- reason - activity in faecal sample effects hormones concentrations if not frozen
Reproductive state (affecting hormone data interpretation)
- (Fürtbauer et al., 2014, PNEC) - Macaca assamensis, glucocorticoid hormone
- (Christensen et al., 2022) - fGCs and uGCs
- pregnant = highest glucocorticoids, then lactating, then cyclic, then acyclic
- Pregnant = highest fGCs/uGCs, then lactating, then cycling
Validation:
Laboratory validation
demonstrate that the target hormone is precisely measured (specificity, sensitivity, accuracy and precision of measurements)