TY - JOUR
T1 - Effects of thyroxine on the photoperiodic control of energy balance and reproductive status in Siberian hamsters
AU - O'Jile, Judith R.
AU - Bartness, Timothy J.
N1 - Funding Information:
Adult male Siberian hamsters (2-3 months old) were obtained from our colony that was derived from original breeding stock supplied to Bruce Goldman (University of Connecticut, Storrs) from Dr. Klaus Hoffmann (MPG Clinical Research Unit for Reproductive Medicine, Munster, FRG). The colony was This research was supported by NIH RO-1 DK35254 and NIMH Research Scientist Development Award KO-00841. Requests for reprints should be addressed to T. J. Bartness.
PY - 1992/8
Y1 - 1992/8
N2 - Siberian hamsters (Phodopus sungorus sungorus) exhibit a variety of seasonal responses when exposed to short days (SD), including decreases in body weight and fat, gonadal regression, and changes in several nonsteroid serum hormone concentrations. One such SD-induced hormonal change is a modest decrease in serum thyroxine (T4) concentrations. In an attempt to determine any underlying hormonal influences for the SD-induced decreases in body weight and fat, we investigated the possible role of T4 and triiodothyronine (T3). This potential paradoxical effect of these hormones on body weight and fat, as compared with most other rodent species, is not without precedent in Siberian hamsters. Specifically, changes in the gonadal steroids have opposite effects on body weight and fat in Siberian hamsters compared with laboratory rats and mice, and Syrian hamsters. SD serum thyroid hormone concentrations were elevated to long-day (LD) levels via subcutaneous T4 injections. Vehicle- and noninjected controls were included, as well as three similar LD-housed groups. Although we found a trend towards decreased T4 serum concentrations in noninjected control hamsters following 9 weeks of SD exposure, this effect did not reach statistical significance. SD-housed, T4-injected hamsters had similar decreases in body, fat pad, and paired testes weights compared to the SD-housed, vehicle- and noninjected controls despite having LD-like serum T4 and T3 concentrations. Thus, no paradoxical effect of the thyroid hormones on body weight (fat) was found, nor do these hormones appear to play a role in the effects of SDs on reproductive status in this hamster species.
AB - Siberian hamsters (Phodopus sungorus sungorus) exhibit a variety of seasonal responses when exposed to short days (SD), including decreases in body weight and fat, gonadal regression, and changes in several nonsteroid serum hormone concentrations. One such SD-induced hormonal change is a modest decrease in serum thyroxine (T4) concentrations. In an attempt to determine any underlying hormonal influences for the SD-induced decreases in body weight and fat, we investigated the possible role of T4 and triiodothyronine (T3). This potential paradoxical effect of these hormones on body weight and fat, as compared with most other rodent species, is not without precedent in Siberian hamsters. Specifically, changes in the gonadal steroids have opposite effects on body weight and fat in Siberian hamsters compared with laboratory rats and mice, and Syrian hamsters. SD serum thyroid hormone concentrations were elevated to long-day (LD) levels via subcutaneous T4 injections. Vehicle- and noninjected controls were included, as well as three similar LD-housed groups. Although we found a trend towards decreased T4 serum concentrations in noninjected control hamsters following 9 weeks of SD exposure, this effect did not reach statistical significance. SD-housed, T4-injected hamsters had similar decreases in body, fat pad, and paired testes weights compared to the SD-housed, vehicle- and noninjected controls despite having LD-like serum T4 and T3 concentrations. Thus, no paradoxical effect of the thyroid hormones on body weight (fat) was found, nor do these hormones appear to play a role in the effects of SDs on reproductive status in this hamster species.
KW - Food intake
KW - Hamsters
KW - Thyroid
KW - White adipose tissue
UR - http://www.scopus.com/inward/record.url?scp=0026669920&partnerID=8YFLogxK
U2 - 10.1016/0031-9384(92)90269-8
DO - 10.1016/0031-9384(92)90269-8
M3 - Article
C2 - 1523252
AN - SCOPUS:0026669920
SN - 0031-9384
VL - 52
SP - 267
EP - 270
JO - Physiology and Behavior
JF - Physiology and Behavior
IS - 2
ER -