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Table 2 Overview of reproductive and metabolic hormones in captive African elephants and Asian elephants

From: Clinical health issues, reproductive hormones, and metabolic hormones associated with gut microbiome structure in African and Asian elephants

Reproductive hormones

Function

African (n = 61)

Asian (n = 38)

Progestagens (ng/ml)

Produced by the corpora lutea of ovary, involved in pregnancy and menstrual cycle, concentrations increase after ovulation

Continuous

Range: 0.052–0.607

Median: 0.17

Mean: 0.21

Continuous

Range: 0.052–0.562

Median: 0.25

Mean: 0.25

Prolactin

PRL (ng/ml)

Produced by the anterior pituitary, promotes lactation, involved in normal follicular function, maintains homeostasis [118, 119]

Continuous

Range: 2.44–105.24

Median: 11.57

Mean: 17.40

Continuous

Range: 2.34–21.26

Median: 5.25

Mean: 6.30

Luteinizing hormone

LH (ng/ml)

Produced by the anterior pituitary, initiates ovulation, develops and maintains corpus luteum

Continuous

Range: 0.59–2.64

Median: 0.99

Mean: 1.08

Continuous

Range: 0.47–3.45

Median: 1.24

Mean: 1.36

Follicle-stimulating hormone

FSH (ng/ml)

Produced by the anterior pituitary, promotes follicular development

Continuous

Range: 1.07–5.53

Median: 2.66

Mean: 2.73

Continuous

Range: 2.84–7.38

Median: 4.11

Mean: 4.42

Metabolic hormones

Function

African (n = 61)

Asian (n = 38)

Fecal glucocorticoid metabolites

FGM (ng/g)

Produced by the adrenal cortex; functions in metabolizing carbohydrates, proteins, and fats [45, 46], induces glucose synthesis [47]. Often used as a measure of chronic physiological stress in wildlife [48]

Continuous

Range: 21.02–249.53

Median: 84.22

Mean: 93.68

Continuous

Range: 20.92–328.29

Median: 108.20

Mean: 128.13

Thyroid stimulating hormone

TSH (ng/ml)

Produced by the anterior pituitary, TSH stimulates the thyroid gland to produce T4, which can be transformed into T3 [120]

Continuous

Range: 0.19–1.73

Median: 0.85

Mean: 0.88

Continuous

Range: 0.12–1.88

Median: 1.04

Mean: 1.07

Total triiodothyronine

Total T3 (ng/dl)

 

Continuous

Range: 38.04–117.64

Median: 85.7

Mean: 85.52

Continuous

Range: 52.06–165.89

Median: 95.97

Mean: 98.38

Total thyroxine

Total T4 (µg/dl)

Produced by the thyroid gland, T4 and T3 control metabolism, homeostasis, and growth [121, 122]. T4 and T3 circulate in plasma bound to transport protein and unbound. Unbound hormone is referred to as “free”, whereas “total” measures bound and unbound hormone. Free T4 moves to target organs where it is transformed to T3

Continuous

Range: 6.77–14.72

Median: 9.46

Mean: 9.75

Continuous

Range: 6.48–12.64

Median: 10.02

Mean: 10.20

Free thyroxine

Free T4 (ng/dl)

Continuous

Range: 0.49–1.17

Median: 0.84

Mean: 0.83

Continuous

Range: 0.44–1.23

Median: 0.71

Mean: 0.75

  1. Description of general function and range of reproductive and metabolic hormones in African and Asian elephants (dataset includes zoos with two or more elephants)