Physilogical cahnges in TSH in early preg due tosimilarity of hCG &TSH receptors.

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·         Pregnancy & Thyroid physiology:-What is the Normal TSH variations in Pregnancy?? Q.1:-What changes in TSH value occur in occur in early months pregnancy ?? Ans:TSH usually falls , Q.2: Why TSH usually falls?? Ans :-Serum TSH level falls in the 1st trimester of normal pregnancies as a physiological response to the stimulating effect of hCG on the TSH receptor with a peak hCG level between 7 and 11 weeks. Q3. What is the maximum lower limit of TSH?? Ans:- Therefore,  normal TSH level can be as low as .03 or even undetectable in early pregnancy as thyrotrophic activity of HCG can suppress TSH .If subnormal then one has to assess  serum FT4 and  any subnormal TSH value should be evaluated in conjunction with serum FT4 level,

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·         Q. 4:-When one diagnoses as hyperthyroidism?? Ans:-The diagnosis of clinical hyperthyroidism is made in the presence of suppressed or undetectable TSH & an elevated FT4 level

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Q. 5; What is sub clinicalhypothyroidism ?? Does women in preg who exhibit normal T3 and T4 warrant replacement?? Ans: One has to assess TPO ab as well and then only one can answer. - Subclinical Hypothyroidism ( SCH) during pregnancy is defined as TSH between
2.5 & 10  mIU/L with a normal FT4 level & F T3 ... In this situation one should insist on   TPO antibodies.  Subclinical hypothyroidism and needs treatment.

Q.6: What is target level of TSH in preg?? Ans:-Goal in pregnancy is to keep TSH below 2.5 especially in first trimester. The foetus is totally dependant on maternal thyroxine till 12 weeks because the fetal thyroid starts functioning only after 12 weeks.

Q.7 : Deficiency earlier what will be the adverse effects ?? Ans:-to that can lead to mental retardation. This is subclinical hypothyroidism n needs treatment with thyroxine. Second trimester TSH value should be less than 3.0

Q.8 :-What is Overt Hypothyroidism ( OH)..??.Any TSH > than 10 mIU/L irrespective of FT4 level or elevated TSH value ( > than 2.5) together with decreased FT4 level is known as Overt Hypothyroidism ( OH)..

Q.9:-Does  newly diagnosed SCH during pregnancy warrant Tr with LT4 ( thyroxine) ?? Ans; There is no consensus on this issue. American Thyroid association ( ATA) recommends that newly diagnosed cases of SCH be tested for TPO Ab..Women who are +ve for TPO Ab & have SCH should be treated with LT4?? ..There is insufficient evidence to recommend for or against universal LT4 treatment in TPOAb -ve pregnant women with SCH . As  such as there is no consensus so may  or may not treat ... Left on treating doctors ( ATA recommendations)...

.Q.10:-Dose of replacement?? Ans:-European thyroid Association ( ETA) & Indian thyroid Association ( ITS) recommends treating newly diagnosed SCH during pregnancy with LT4 ( thyroxine)  What will be the  starting dose ?? it will be of 1 to 1.2 microgram / Kg / day is advised in cases of SCH ...).  

Q.11:-Take home message :-Elevation of TSH during pregnancy should be defined using pregnancy specific ranges.What is the trimester specific targets? Such are  :

.1 to 2.5 in first trimester

.2 to 3 in 2nd trimester

.3 to 3 mIU/Lin 3rd trimester

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·         Advantage for thyroxine like Vit D:-- Thyroxine has a wide safety factor and should be started for subclinical hypothyroidism