Effect of Thyroid Hormone Deficiency on Glycosylation of Rat TSH Secreted<i>In Vitro</i>

Harel, Gideon; Jp, Kane; Ds, Shamoun; Ja, Magner; Szabó, Márta

doi:10.1055/s-2007-1002097

Cited by 5 publications

(3 citation statements)

References 8 publications

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“…In patients with hypothyroidism or thyroid hormone resistance, the explanation to highly sialylated TSH has been the early expression of a-2,6-sialyltransferase activity in thyrotrophs (19,30). Hypothyroidism in rats induced the biosynthesis of a TSH molecule with increased content of biantennary complex oligosaccharides and reduced amount of high mannose/hybrid oligosaccharides (31). The glycosylation of another glycoprotein, a-lactalbumin, is also under the control of thyroid hormones.…”

Section: Discussionmentioning

confidence: 99%

Characterization of Sex Hormone-Binding Globulin Isoforms in Hypothyroid Women

Brenta

Bedecarrás

Schnitman

et al. 2002

Thyroid

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Liver sex hormone-binding globulin (SHBG) biosynthesis is regulated by triiodothyronine (T3). This regulation is responsible for increased serum SHBG concentrations in hyperthyroid states. However, in hypothyroidism, normal SHBG levels are frequently found. To understand this we have characterized circulating SHBG isoforms according to their sialic acid content, which determines its half-life, in euthyroid and hypothyroid women. Six euthyroid (aged 56 +/- 8 years) and five hypothyroid women (51 +/- 13 years) were studied. Their body mass index (BMI) range was 20-25. Hypothyroidism diagnosis was based on clinical findings, elevated basal thyrotropin (TSH) and decreased T3 and thyroxine (T4) values. Total SHBG was measured by radioimmunoassay (RIA) and SHBG isoforms were isolated using preparative isoelectrofocusing. For comparisons, two-tailed t test was applied. No statistical difference was found between the total SHBG levels of hypothyroid and euthyroid postmenopausal women. Three groups of SHBG isoforms were isolated in the euthyroid group: S(I): pl: 5.0-5.2: 20% +/- 4%, S(II) : pl 5.2-5.4: 50% +/- 3% and S(III): pl 5.4-5.6: 29% +/- 4%. In hypothyroid patients, although the three groups of isoforms were isolated in the same pH range, S(I) and S(II) proportions were different (p < 0.001) when compared to normal women: S(I): 34% +/- 4%, S(II): 33% +/- 9.9% and S(III): 29% +/- 5.7%. These results show that hypothyroid patients have a higher proportion of more acidic SHBG isoforms. This variation may explain the normal levels of serum SHBG observed in hypothyroidism.

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Section: Discussionmentioning

confidence: 99%

Characterization of Sex Hormone-Binding Globulin Isoforms in Hypothyroid Women

Brenta

Bedecarrás

Schnitman

et al. 2002

Thyroid

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“…However, TRH also affects the post‐translational glycosylation of TSH which affects its biological activity. 132–137 Interestingly, a recent report by Nikrodhanond et al 138 . demonstrates that the role of TRH in regulating the pituitary‐thyroid axis is stronger than the role of TH negative feedback.…”

Section: Thyroid Hormone Insufficiency—to What Extent Can Compensatormentioning

confidence: 99%

Collision of Basic and Applied Approaches to Risk Assessment of Thyroid Toxicants

THOMAS ZOELLER

2006

Annals of the New York Academy of Sciences

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Thyroid hormone (TH) is essential for normal brain development; therefore, any environmental chemical that interferes sufficiently with thyroid function, TH metabolism, or TH action may exert adverse effects on brain development. Important known differences in aspects of thyroid endocrinology between the fetus, infant, and adult allow us to identify age-dependent vulnerabilities to thyroid toxicants with some confidence. These differences include the size of the hormone pool stored in the thyroid gland at different ages as well as the age-dependent sensitivity to mild TH insufficiency. Several recent studies that describe risk assessments of the environmental contaminant, ammonium perchlorate, provide good examples of conclusions based on the selective consideration of these known aspects of the thyroid system. Specifically, authors who consider age-dependent differences in thyroid endocrinology suggest that safe levels of perchlorate should be set at relatively low levels (low parts per billion). In contrast, authors who do not consider these known age-dependent differences in thyroid endocrinology recommend safe levels of perchlorate at high (hundreds) parts per billion to parts per million. Emerging evidence indicates that a variety of high production volume chemicals can directly interact with the TH receptor. As testing paradigms are designed by regulatory agencies, these age-dependent differences in thyroid endocrinology must be considered.

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“…( 246 ) However, TRH also affects the post‐translational glycosylation of TSH, which affects its biological activity. ( 247‐252 ) 3. Pituitary TSH is one of three glycoprotein hormones of the pituitary gland and is composed of an alpha and a beta subunit.…”

Section: Endocrinology Of the Thyroid Systemmentioning

confidence: 99%

Challenges Confronting Risk Analysis of Potential Thyroid Toxicants

Zoeller¹

2003

Risk Analysis

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Screening and testing for potential thyroid toxicants using endpoints of thyroid function, including circulating levels of thyroid hormones and thyrotropin, will not capture toxicants that directly interfere with thyroid hormone action at the receptor. The goals of the present review are to provide a critique of the literature focused on thyroid hormone and brain development as it relates to testing and evaluating thyroid toxicants, and to propose possible solutions to this perceived dilemma.

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Effect of Thyroid Hormone Deficiency on Glycosylation of Rat TSH SecretedIn Vitro

Cited by 5 publications

References 8 publications

Characterization of Sex Hormone-Binding Globulin Isoforms in Hypothyroid Women

Characterization of Sex Hormone-Binding Globulin Isoforms in Hypothyroid Women

Collision of Basic and Applied Approaches to Risk Assessment of Thyroid Toxicants

Challenges Confronting Risk Analysis of Potential Thyroid Toxicants

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