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    Proc Soc Exp Biol Med. 1987 Feb;184(2):144-50.

    Serum concentrations of thyroid hormones and extrathyroidal thyroxine-5'-monodeiodinase activity during lactation in the rat.

    Kahl S, Capuco AV, Bitman J.

    Serum thyroxine (T4) and triiodothyronine (T3) concentrations and T4-5'-monodeiodinase activity in liver and kidney homogenates were studied in Sprague-Dawley rats during lactation. Blood and tissue samples were collected from nulliparous and pregnant rats 2 days before delivery and from lactating rats 0, 2, 7, 12, 19, and 26 days after delivery. Litters were removed from half of the mothers immediately after delivery to create a postpartum nonlactating group for study at the same times. Pregnant rats had lower serum T4 and T3 concentrations and higher liver T4-5'-monodeiodinase activity than nulliparous females. Low serum T4 persisted throughout lactation but further decrease in serum T3 was observed. Activity of T4-5'-monodeiodinase in liver and kidney homogenates was significantly reduced during lactation as compared to nonlactating rats. Serum concentration of T4 and T3 and T4-5'-monodeiodinase activity in liver and kidney returned toward control values 5 days after weaning (Postpartum Day 26). Our findings suggest that the relative hypothyroid state observed during lactation in rats is associated with a significant decrease in T4 to T3 conversion in the liver and kidneys.

    PMID: 3809169 [PubMed - indexed for MEDLINE]

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    Patient drug information

    • Thyroid (Armour® Thyroid)

      Thyroid is a hormone produced by the body. When taken correctly, thyroid is used to treat the symptoms of hypothyroidism (a condition where the thyroid gland does not produce enough thyroid hormone). Symptoms of hypothyr...

    • Levothyroxine (Levothroid®, Levoxyl®, Synthroid®, ...)

      Levothyroxine, a thyroid hormone, is used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormone. Without this hormone, the body cannot function properly, resulting in poor g...

    • Liothyronine (Cytomel®)

      Liothyronine, a thyroid hormone, is used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormone. Without this hormone, the body cannot function properly, resulting in poor gr...