Impaired action of thyroid hormone associated with smoking in women with hypothyroidism

Article Abstract:

Smoking may reduce both the production and physiologic action of thyroid hormone. Thyrotropin from the pituitary gland stimulates the thyroid gland to produce thyroxine, which in turn is converted to active thyroid hormone, known as triiodothyronine. Researchers measured the levels of all of these hormones in 138 women with normal thyroid function, 84 with asymptomatic hypothyroidism, and 51 with symptomatic hypothyroidism. Among the normal women and those with symptomatic hypothyroidism, hormone levels were the same in non-smokers and smokers. However, among the women with asymptomatic hypothyroidism, smokers had higher cholesterol and thyrotropin levels and higher ratios of triiodothyronine to thyroxine. These comparisons indicate that smoking harms the thyroid gland and inhibits the action of thyroid hormone on cells. These effects of smoking may not be apparent in women with advanced hypothyroidism because their thyroid gland is already damaged.

Physiological aspects, Smoking, Hypothyroidism

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Maternal-fetal transfer of thyroxine in congenital hypothyroidism due to a total organification defect or thyroid agenesis

Article Abstract:

Hypothyroidism is an inherited disorder caused by partial or total lack of thyroid organ development. When infants are born without thyroid function, they initially appear normal. However, within a few weeks their condition deteriorates and signs of decreased or absent thyroid function (hypothyroidism) become obvious. It is suggested that these infants do not appear with symptoms initially because thyroid hormones may be passed from the mother during pregnancy. To determine if the hormone thyroxine (T4) is transferred from the mother, 25 newborns born in the Netherlands were tested for T4 blood levels. The results revealed that T4 was transferred from the mother to the fetus, which in turn remained in the fetus for an average of 3.5 days. It is estimated that this transfer of thyroxine occurred in the later part of the pregnancy.

Analysis, Case studies, Abnormalities, Maternal-fetal exchange, Infants (Newborn), Newborn infants, Congenital hypothyroidism

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Effects of thyroxine supplementation on neurologic development in infants born at less than 30 weeks' gestation

Article Abstract:

Thyroxine treatment does not appear to benefit infants born between 27 and 30 weeks' gestation but it may benefit those born before 27 weeks. Researchers randomly assigned 200 premature infants to receive daily thyroxine or placebo shortly after birth for 6 weeks. Their development was assessed at 6, 12 and 24 months using tests that measure mental and psychomotor development. Among the 157 infants tested at 24 months, thyroxine made no difference in development except in those born before 27 months.

Evaluation, Infants (Premature), Premature infants, Growth, Nervous system, Infant development

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