Thyroid disease and pregnancy
David S. Cooper, Jennifer A. Sipos in Medical Management of Thyroid Disease, 2018
The activity of Graves’ disease fluctuates through pregnancy with thyroid stimulating hormone (TSH) receptor antibody patterns generally reflecting the clinical course of the disease. The clinician must be able to differentiate normal physiological changes from true thyroid disease; however, hyperthyroidism and hypothyroidism may first be detected during pregnancy. Euthyroid women with detectable antithyroid antibodies may have slightly higher first trimester serum TSH values, remaining within the normal range, compared to normal pregnant controls. Levothyroxine replaced hypothyroid women should have thyroid function monitored as they become pregnant and again every 4–6 weeks in the first half of pregnancy. Antithyroid drugs (ATD) are the main treatment for Graves’ disease during pregnancy. Propylthiouracil and methimazole have both been used during gestation. ATD therapy may be stopped preconception or during early pregnancy in women with active Graves’ disease who are euthyroid while taking low doses of ATD.
Iodine is needed to maintain health
Tatsuo Kaiho in Iodine Made Simple, 2017
Halogens (fluorine, chlorine, bromine, iodine) play an important role in the field of pharmaceuticals. Idoxuridine is an antivirus ophthalmic solution and is generally used as a therapeutic drug for keratitis occurring resulting from inflammation due to viral infection. Levothyroxine is the oldest iodine-containing drug used as a thyroid hormone agent. There are two types of thyroid hormones, namely triiodothyronine (T3) and thyroxine (T4). T3 activity is said to be several times stronger than T4. Iodine is indispensable in X-ray contrast agents. Thyroid hormones are comprised of iodine. Sterilizing agents commonly used in hospitals include benzalkonium chloride, chlorohexidine gluconate, and povidone iodine. X-ray contrast agents are widely used for cardiovascular and cerebrovascular examinations and other detailed examinations performed in hospitals. In most cases, iodine-based drugs are used. One-third of radiopharmaceuticals are of iodine compounds. Radioactive iodine compounds can diagnose illnesses. Cadexomer iodine is used for bedsores. Iodine-based sterilizers are multidrug resistant.
Congenital hypothyroidism
Pallavi Iyer, Herbert Chen in Thyroid and Parathyroid Disorders in Children, 2020
Thyroid hormone is essential for normal development, especially during the first several years of life when crucial brain and somatic growth are in progress. Since its inception in developed countries during the 1970s, newborn screening (NBS) for congenital hypothyroidism (CH) has essentially eradicated the neurocognitive disability of this condition. CH encompasses disorders of the thyroid gland (primary hypothyroidism) and pituitary/hypothalamic axis (central hypothyroidism). Early detection and treatment of CH by NBS avert the classic clinical phenotype of CH and its serious neurodevelopmental sequelae. The classic clinical findings of severe, untreated CH are uncommon due to early detection but can include prolonged jaundice, cold and mottled skin, large tongue, umbilical hernia, facial puffiness, and open posterior fontanelle. Once confirmatory serum labs are obtained on a newborn with suspected CH, treatment should begin promptly with 10–15 mcg/kg/day of oral levothyroxine. The highest dose range is recommended for infants with severe hypothyroxinemia.
Impact of hydration state and molecular oxygen on the chemical stability of levothyroxine sodium
Published in Pharmaceutical Development and Technology, 2015
Mazen Lee Hamad, William Engen, Kenneth R. Morris
Levothyroxine sodium is an important medication used primarily for treating patients with hypothyroidism. Levothyroxine sodium tablets have been recalled many times since their 1955 introduction to the US market. These recalls resulted from the failure of lots to meet their content uniformity and potency specifications. The purpose of this study is to test the hypothesis that the chemical stability of levothyroxine sodium pentahydrate is compromised upon exposing the dehydrated substance to molecular oxygen. The impact of temperature, oxygen and humidity storage conditions on the stability of solid-state levothyroxine sodium was examined. After exposure to these storage conditions for selected periods of time, high performance liquid chromatography (HPLC) was used to quantify the formation of impurities. The results showed that levothyroxine sodium samples degraded significantly over a 32-day test period when subjected to dry conditions in the presence of molecular oxygen. However, dehydrated samples remained stable when oxygen was removed from the storage chamber. Furthermore, hydrated samples were stable in the presence of oxygen and in the absence of oxygen. These results reveal conditions that will degrade levothyroxine sodium pentahydrate and elucidate measures that can be taken to stabilize the drug substance.
A new formulation of levothyroxine engineered to meet new specification standards
Published in Current Medical Research and Opinion, 2019
Hans-Peter Lipp, Ulrike Hostalek
Background: Small variations in the dose of levothyroxine have been associated with marked variations in thyroid function in people with hypothyroidism. Accordingly, regulators have identified levothyroxine as a “narrow therapeutic index” drug subject to more stringent regulations compared with other drugs, in terms of the accuracy and stability of the amount of active drug in each tablet (typically required to be 95–105% of the labelled amount over its full shelf life), and its bioavailability geometric mean ratios (90% confidence intervals between 90–111.1%, including 100%). Review: This review describes a reformulation of a widely used levothyroxine product (Euthyrox.*). The new tablet fulfils all criteria according to the new specification regulations for dosage accuracy over a shelf life of 3 years in all climate zones, and for bioequivalence compared to the conventional formulation used for many years. In addition, a clinical trial demonstrated equivalent exposure between three different tablet strengths of the new formulation, amounting to the same total dose (dose form proportionality). As a consequence, switching from the conventional to the new formulation can be undertaken on a 1:1 dose-for-dose basis, without re-titration or additional thyroid function testing. Conclusion: The new formulation, which is more stable, will assist in the accurate dosage and titration of levothyroxine in the management of hypothyroidism.
Nongenomic effect of levothyroxine on the synchronous electrical activity of the spinal dorsal horn in the rat
Published in Somatosensory & Motor Research, 2014
Verónika Storaci, Antonio Eblen-Zajjur
Levothyroxine (T4) has a well-known effect on the central nervous system (CNS). This effect requires hours of latency by genetic pathway. We tested for short latency nongenomic effects of T4 superfusion on the spinal dorsal horn (DH) evaluating lumbar somatosensory evoked potentials in rats. T4 increased N and P wave amplitudes and N wave area under the curve, but reduced P wave duration and N–P interval, suggesting that T4 exerts both excitatory and synchronizing effects on DH interneurons in less than 300 s, thus, providing evidence of nongenomic effects of T4 on DH.
Related Knowledge Centers
- Thyroid Hormones
- Thyroxine
- Triiodothyronine
- Thyroid Gland
- Aromatic Amino Acids
- Monoiodotyrosine
- Diiodotyrosine