Effects of Osteoporotic Cytokines in Ovary-Intact and Ovariectomised Rats with Induced Hyperthyroidism; Is Skeletal Responsiveness to Thyroid Hormone Altered in Estrogen Deficiency ?

Effects of Osteoporotic Cytokines in Ovary-Intact and
Ovariectomised Rats with Induced Hyperthyroidism;
Is Skeletal Responsiveness to Thyroid Hormone
Altered in Estrogen Deficiency ?

GÖNÜL SIMSEK, HAFIZE UZUN,¹ YESARI KARTER,²
SEVAL AYDIN¹ and GÜNNUR YIGIT

Department of Physiology, ¹Department of Biochemistry, ²Department of Internal Medicine, Cerrahpasa Faculty of Medicine, Istanbul University, Istanbul, Turkey

This experimental study was designed to examine the effects of hyperthyroidism on osteoporotic cytokines such as interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α in the physiological concentrations and in the deficiency of estrogen. We investigated the effects of thyroid hormones on cytokines and bone metabolism in L-thyroxine induced ovary-intact and ovariectomised rats, as levels of cytokines were increased in hyperthyroidism. The rats were divided into three groups. In the first group, L-thyroxine-induced hyperthyroid rats were ovariectomised (OVX), while the OVX rats were administered L-thyroxine in the second group. The third group received sham-operation. Blood samples taken from the tail vein of rats were analyzed for plasma T₃, T₄, TSH and serum IL-1β, IL-6, TNFα, calcium (Ca), phosphorous (P), parathyroid hormone (PTH), alkaline phosphatase (ALP), bone-specific alkaline phosphatase (b-ALP). L-thyroxine administration increased the cytokines, ALP and b-ALP and decreased PTH, while there was no change in Ca and P. However, the ovariectomy of these rats did not change the levels of cytokines, Ca, P, PTH, ALP, and b-ALP. In ovariectomised rats, the cytokines, ALP and b-ALP increased but not Ca and P conversely, PTH decreased. L-thyroxine administration to ovariectomised rats did not change the levels of cytokines, Ca, P, PTH, ALP and b-ALP. In sham-operated rats there was no change in any of the parameters compared with initial values. Thyroid hormones may not be effective on bone metabolism in estrogen deficiency.

keywords —— hyperthyroidism; ovariectomy; interleukin-1β; interleukin-6; tumor necrosis factor-α

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Tohoku J. Exp. Med., 2003, 201, 81-89

Address for reprints: Gönül Simsek, 1. Ulus Mah. Portakal Yokusu, Gürcü Kizi Çikmazi, Sayhan Sitesi CB-10 Ulus, Besiktas, Istanbul, Turkey.

e-mail: gdincsimsek@yahoo.com