Table 4.

Summary of some reproductive factors influencing bone and fat metabolism in hibernators^a

Hormone	Species	Seasonal concentrations					References
		Fall (pre-hibernation)	Winter (hibernation)		Spring (post-hibernation)	Summer (active)
			Early hibernation	Late hibernation
Estrogens	American Black Bear (U. americanus)	19–25 pg/ml	25–27 pg/ml		20–44 pg/ml	44–70 pg/ml	Tsubota et al. (1997)
	European Ground Squirrel (S. citellus)	120 pg/ml			198 pg/ml	330 pg/ml	Millesi et al. (2008)
	Greater Asiatic Yellow Bat (S. heathi)	250.43 pg/ml	197.9 pg/ml	51.9 pg/ml	182.1 pg/ml	119.05 pg/ml	Krishna and Abhilasha (2000)
Prolactin	Japanese Black Bear (U. thibetanus japonicas)	2.24 ng/ml	7.96 ng/ml	8.14 ng/ml	8.4–9.1 ng/ml	8.67 ng/ml	Sato et al. (2001) and Howell-Skalla et al. (2000)
	Woodchuck (M. monax)	0.2–1.3 ng/ml	2.35 ng/ml		7.0–20.7 ng/ml		Concannon et al. (1999)
Testosterone	American Black Bear	0.1–2.0 ng/ml	1.0 ng/ml	2.4 ng/ml	0.6–12.4 ng/ml	12.4–63.2 ng/ml	Tsubota et al. (1997) and Tsubota et al. (1999)
	Woodchuck	0.1–0.2 ng/ml	1.0 ng/ml	3.4–6.6 ng/ml	0.6–1.0 ng/ml	0.1–0.2 ng/ml	Concannon et al. (1999) and Baldwin et al. (1985)
	Hedgehog (E. europaeus)	1.33 pg/ml	17.9 pg/ml		17.9 pg/ml		Saboureau (1986)
	Golden-mantled Ground Squirrel (C. lateralis)	0.061 ng/ml	0.063 ng/ml		8.824 ng/ml		Barnes (1986)

^aThis table reflects a summary of key studies in hibernation with potential insight into bone metabolism. The table is not intended to be all inclusive and the ranges given do not highlight seasonal changes that may be found in particular studies.