Abstract

Intact mouse thyroid glands were used to measure the formation of cyclic [3H]AMP from [3H]adenine, and the release of thyroidal iodine. These two parameters of thyroid activity responded to similar concentrations of thyroid-stimulating hormone (TSH). Both were stimulated by prostaglandin E1, although the response was always very much less than to TSH. Both were inhibited by NaF, which appeared to have a toxic effect on the gland. The response to TSH was in each case reduced by lithium, suggesting that the antithyroid effect of Li+ is associated with a direct action on adenyl cyclase; however, Li+ also reduced thyroidal hormone secretion induced by dibutyryl cyclic AMP and may therefore have a second site of action. In general, the effects of these agents on cyclic [3H]AMP formation correlated well with their effects on thyroidal iodine release. The results support the hypothesis that the activation of adenyl cyclase is closely associated with, and precedes, thyroid hormone secretion.

• Related Studies :

  • Inhibition of thyroid secretion by sodium fluoride in vitro

    NaF mimicked the activation by thyrotropin of iodide binding to proteins and of glucose C-r oxidation but not the accumulation of intracellular colloid droplets or the stimulation of secretion in dog thyroid slices in vitro. On the contrary, NaF inhibited the two latter thyrotropin effects. The inhibitory action of F-

  • Is water fluoridation a hidden cause of obesity? Histological study on thyroid follicular cells of albino rats

    Introduction: Fluoride in drinking water is known to exert both beneficial and detrimental effects on health. When consumed in excess, it is known to cause adverse effects including dental fluorosis, hip fracture, bone cancer, lower intelligence, and kidney toxicity plus goiter. Aim: This study was carried out to determine the histological

  • y-Aminobutyric acid ameliorates fluoride-induced hypothyroidism in male kunming mice

    AIM:  This study evaluated the protective effects of y-aminobutyric acid (GABA), a non-protein amino acid and anti-oxidant, against fluoride-induced hypothyroidism in mice. MAIN METHODS:  light microscope sample preparation technique and TEM sample preparation technique were used to assay thyroid microstructure and ultrastructure; enzyme immunoassay method was used to assay hormone and

  • The effects and underlying mechanism of excessive iodide on excessive fluoride-induced thyroid cytotoxicity

    In many regions, excessive fluoride and excessive iodide coexist in groundwater, which may lead to biphasic hazards to human thyroid. To explore fluoride-induced thyroid cytotoxicity and the mechanism underlying the effects of excessive iodide on fluoride-induced cytotoxicity, a thyroid cell line (Nthy-ori 3-1) was exposed to excessive fluoride and/or excessive

  • Role of endoplasmic reticulum stress-induced apoptosis in rat thyroid toxicity caused by excess fluoride and/or iodide

    Excess fluoride and iodide coexist in drinking water in many regions, but few studies have investigated the single or interactive effects on thyroid in vivo. In our study, Wistar rats were exposed to excess fluoride and/or iodide through drinking water for 2 or 8 months. The structure and function of

• Related FAN Content :

  • Fluoride's Impact on Thyroid Hormones

    Up through the 1950s, doctors in Europe and South America prescribed fluoride for this purpose in patients with hyperthyroidism. (Merck Index 1968). Fluoride was selected as a thyroid suppressant based on findings dating back to the mid-19th century that fluoride is a goitrogen (a substance that can cause goiter). When used as

  • Fluorine in the Aetiology of Endemic Goitre

    The distribution of endemic goitre in the Punjab and in England is related to the geological distribution of fluorine and to the distribution of human dental fluorosis (mottled enamel). Inquiry showed the presence of dental fluorosis among school-children in two areas of Somerset where two previous observers had recorded a high incidence of goitre, and the absence of dental fluorosis in an adjoining area selected as control where endemic goitre was absent.

  • Fluoride Aggravates Thyroid Damage Caused by Excess Iodine Intake

    Chinese researchers have found that the combination of excess fluoride with excess iodine caused greater reductions in IQ, or greater increases in goitre than either scenario by itself.

  • Fluoride & Goiter

    Goitre (aka goiter) is an enlargement of the thyroid gland that in some cases can produce visible swelling in the neck. The main cause of goitre is iodine deficiency. Goitre can also be caused by other things, including hypothyroidism and substances that cause goitre (goitrogens). Since as far back as the

  • Mikhailets (1996): Functional state of thyroid under extended exposure to fluorides

    Abnormalities in the thyroid function characterized by a decreased iodine absorption function of the thyroid, a low level T3 syndrome, and a slight increase of the TSH level are observed in cases of chronic fluorine intoxication in the industrial workers.