OBJECTIVE: To observe the effects of levothyroxine sodium tablets on vitamin D and bone metabolism indexes in pregnant women with subclinical hypothyroidism at the second trimester. METHODS: Totally 90 pregnant women with subclinical hypothyroidism at the second trimester admitted into the First Central Hospital of Baoding from Jan. 2017 to Dec. 2018 were extracted to be divided into the treatment group and the control group according to whether or not levothyroxine sodium tablets were used

with 45 cases in each group. The treatment group was treated with Levothyroxine sodium tablets

and patients’ thyroid function was reexamined every 4 weeks. The control group only received regular reexamination of thyroid function. Changes in thyroid function

25-hydroxyvitamin D [25-（ OH）-D]

parathyroid hormone（ PTH）

bone gla protein（ BGP）

procollagen type Ⅰ N-terminal propetide（ PⅠNP） and bone mineral density before and after treatment were compared between two groups

and pregnancy outcomes were observed.RESULTS: After treatment of 8 weeks

the levels of thyroid stimulating hormone in the treatment group were significantly lower than those before treatment

and 25-（ OH）-D

BGP

P ⅠNP and bone density were significantly higher than those before treatment

and the differences were statistically significant（ P<0. 05）. The above indicators in the control group showed no significant changes compared with those before treatment

and the differences were not statistically significant（ P>0. 05）

the above indicators in the treatment group were significantly better than those in the control group

with statistically significant differences（ P<0. 05）. The incidence of adverse pregnancy outcomes in the treatment group was 11. 11%（ 5/45）

significantly lower than that in the control group [28. 89%（ 13/45） ]

with statistically significant difference（ P < 0. 05）. CONCLUSIONS: Levothyroxine sodium tablets can effectively reduce TSH levels in patients with subclinical hypothyroidism at the second trimester

regulate bone metabolism and 25-（ OH）-D levels

so as to pregnancy outcomes.