Elevated free thyroxine in newborns

Many parents will give their children a physical examination after they are born to ensure that the baby's body is developing normally. Generally speaking, if a child is given a physical examination, various indicators in the child's body will be checked. Some parents find that their baby's free thyroxine is high after examination, and they worry that it will affect the baby's normal physical development. So, what should we do if the free thyroxine level in newborns is too high?

1. What is the cause of high free thyroxine in newborns?

On the ninth day after the baby was born, the free thyroxine level was slightly high, but the thyrotropin level was too high, indicating the possibility of low thyroid hormone. In the late stage of pregnancy, the mother developed hypothyroidism and had been taking Euthyrox. The mother's body will have an impact on the baby, and hypothyroidism will affect the baby's growth. Because the baby has just been born, if the baby's own thyroid function is normal, he will be normal in the future. Pay attention to follow-up examinations.

2. Normal value of free thyroxine

Thyrotropin-releasing hormone (TRH) normal level: 14-168pmol/L. Free thyroxine index (T4) normal: 2.2-14.0. Thyroid stimulating hormone (TSH)

Normal situation: 3-12mU/L in umbilical cord blood, 0.9-8.1mU/L in children. Free tri-iodothyronine (FT3)

Normal situation: 6.0-11.4pmol/L. Trans-triiodothyronine (anti-T3) normal situation: 0.2-0.8nmol/L. Triiodothyronine (T3 RU)

Normal situation: 0.98-1.00. Total thyroxine (TT4) normal situation: 130-273nmol/L for newborns and 91-195nmol/L for infants. Free thyroxine (FT4)

Normal situation: 26-39pmol/L. Total tri-iodothyronine (TT3) Normal situation: 0.5-1.1nmol/L in umbilical cord blood, 1.4-2.6nmol/L in newborns.

What is free thyroxine?

Thyroxine is a hormone synthesized and secreted by thyroid follicular epithelial cells. Pregnancy, lactation, cirrhosis, nephrotic syndrome, etc. can cause changes in serum thyroxine-binding globulin concentration and its binding capacity, and can cause changes in free thyroxine concentration. The determination of free thyroxine is not affected by serum binding proteins (mainly TBG) and is a sensitive indicator of thyroid function in vitro tests. Even when the serum thyroxine-binding globulin concentration and binding capacity change under physiological and pathological conditions, it can still accurately reflect the function of the thyroid gland.