[Assessment of thyroid hormones and androgens in amniotic fluid: clinical interest]

Ultrasound scanning is able to detect foetal goiter due either to an hypothyroidy either to an hyperthyroidy, or clitoris hypertrophia resulting from adrenal hyperplasia in female, during the second half of pregnancy. The diagnosis of these rare diseases is of interest because the treatment can be started during pregnancy. An amniotic fluid punction can be discussed and its biochemical analysis may be of interest even though very few commercial assays have been tested on amniotic fluid. Our aim was two investigate the practicability and the value of free thyroxin (FT4), thyrotropin (TSH), 17alpha hydroxyprogesterone (17-OHP) and delta 4 androstenedione (Delta4A) measurement on amniotic fluid using commercially available assays for serum. FT4 and TSH are detectable at low levels in amniotic fluid. FT4 significantly increases from 2.1 pmol/L to 4.2 pmol/L while TSH significantly decreases from 0.27 mU/L to 0.12 mU/L during the second half of pregnancy. An increase in amniotic fluid TSH concentration contributes to the diagnosis of foetal hypothyroidy while the measurement of amniotic fluid FT4 is not informative in case of foetal goiter. 17-OHP and Delta4A are present in amniotic fluid at the same level as in serum. 17-OHP significantly decreases from 1.9 ng/mL to 1 ng/mL during the second half of pregnancy while Delta4A significantly increases from 0.5 ng/mL to 0.8 ng/mL. Absence of increase in their concentrations excludes any severe adrenal hyperplasia.