During the study, the researchers involved more than 70000 patients and this is essentially the largest study today where the link between risk of fracture in adult and subclinical hyperthyroidism has been determined. What the team found out in their research is that people having subclinical hyperthyroidism face a much higher risk of any kind of fractures and the risk is even much higher when they have a very low TSH, i.e. <0.1 Miu/l. This is essentially a very clear indication that subclinical hyperthyroidism forms a major risk factor in fractures as the lead author, Nicolas Rodondi noted.

About subclinical hyperthyroidism

Subclinical hyperthyroidism essentially refers to the TSH levels being abnormal in a person but no clinical symptoms are shown and there is normal free thyroxin. The risk of fracture can essentially be affected by thyroid function through thyroid hormones having a direct effect on hormones like osteoblasts and osteoclasts and this in turn results in the rate of bone loss and bone turnover being increased considerably. Hyperthyroidism also has an effect on the coordination and strength of muscles, which can further heighten the risk in case they fall. The authors suggested that thyroxin medication can play a major role in this.

Even though there has been long establishment of the link that exists between a high risk of fractures and osteoporosis and hyperthyroidism, there have been serious difficulties in studying the association that exists between the risk of fracture and hyperthyroidism. As of now, there are no trials that are randomized controlled that have been looking at the issue not to mention that there doesn’t seem like there is any likelihood of one soon. This is largely explained due to the rare nature of subclinical hyperthyroidism and it is such a real problem to find enough participants to undertake a large trial. And besides this, the senior researcher in the team noted that upon detection of the condition, patients are promptly treated and this means that such patients are excluded from trials.

EMBASE and MEDLINE extensively

Given these circumstances, the team undertook a pooled analysis of the large but prospective cohort studies which have tried to ascertain the kind of association that exists between fractures and thyroid function. The team searched EMBASE and MEDLINE extensively to find articles, which had been published up to March 2015 since the sites were incepted, regardless of what language they were written in. in addition, bibliographies were also searched manually to identify key articles that could be of help during the study. Euthyroidism was identified as TSH which ranged from 0.45 to 4.49 Miu/L while subclinical hyperthyroidism was TSH < 0.45 mIU/L which denoted normal levels of thyroxine. After sex and age adjustments were made, people having subclinical hyperthyroidism showed high risk of fracture.