Mohammadi Babak, Haghpanah Vahid, Tavangar Seyed Mohammad, Larijani Bagher
Endocrinology and Metabolism Research Center, Tehran University of Medical Sciences, Tehran, Iran.
Theor Biol Med Model. 2007 Jun 9;4:23. doi: 10.1186/1742-4682-4-23.
The diagnosis, treatment and prevention of osteoporosis is a national health emergency. Osteoporosis quietly progresses without symptoms until late stage complications occur. Older patients are more commonly at risk of fractures due to osteoporosis. The fracture risk increases when suppressive doses of levothyroxine are administered especially in postmenopausal women. The question is; "When should bone mass density be tested in postmenopausal women after the initiation of suppressive levothyroxine therapy?". Standard guidelines for the prevention of osteoporosis suggest that follow-up be done in 1 to 2 years. We were interested in predicting the level of bone mass density in postmenopausal women after the initiation of suppressive levothyroxine therapy with a novel approach.
The study used data from the literature on the influence of exogenous thyroid hormones on bone mass density. Four cubic polynomial equations were obtained by curve fitting for Ward's triangle, trochanter, spine and femoral neck. The behaviors of the models were investigated by statistical and mathematical analyses.
There are four points of inflexion on the graphs of the first derivatives of the equations with respect to time at about 6, 5, 7 and 5 months. In other words, there is a maximum speed of bone loss around the 6th month after the start of suppressive L-thyroxine therapy in post-menopausal women.
It seems reasonable to check bone mass density at the 6th month of therapy. More research is needed to explain the cause and to confirm the clinical application of this phenomenon for osteoporosis, but such an approach can be used as a guide to future experimentation. The investigation of change over time may lead to more sophisticated decision making in a wide variety of clinical problems.
骨质疏松症的诊断、治疗和预防是一项国家卫生紧急事务。骨质疏松症在没有症状的情况下悄然进展，直到出现晚期并发症。老年患者因骨质疏松症更易发生骨折。尤其在绝经后女性中，给予抑制剂量的左甲状腺素时骨折风险会增加。问题是：“绝经后女性开始接受抑制性左甲状腺素治疗后，何时应检测骨密度？”预防骨质疏松症的标准指南建议在1至2年后进行随访。我们有兴趣用一种新方法预测绝经后女性开始接受抑制性左甲状腺素治疗后的骨密度水平。
该研究使用了关于外源性甲状腺激素对骨密度影响的文献数据。通过对沃德三角区、转子、脊柱和股骨颈进行曲线拟合，得到了四个三次多项式方程。通过统计和数学分析研究了模型的行为。
方程一阶导数关于时间的图上在大约6、5、7和5个月时有四个拐点。换句话说，绝经后女性开始接受抑制性左旋甲状腺素治疗后约第6个月左右存在最大骨量流失速度。
在治疗第6个月时检查骨密度似乎是合理的。需要更多研究来解释原因并确认这一现象在骨质疏松症方面的临床应用，但这种方法可作为未来实验的指导。对随时间变化的研究可能会在各种临床问题中带来更精确的决策。
