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A Case-Based Guide to Clinical EndocrinologyIntroduction

A Case-Based Guide to Clinical Endocrinology: Introduction [The thyroid is a highly specialized endocrine gland devoted to the production of thyroid hormones through several enzymatic steps. The thyroid hormones are iodinated derivatives of tyrosine and effect their functions through the interaction with nuclear receptor found in almost every human tissue. The thyroid mostly produces thyroxine, or tetraiodothyronine (T4), an inactive prohormone. The T4 production by the thyroid gland is almost only regulated by the pituitary hormone thyrotropin (TSH), which is in turn also almost only regulated by T4 levels, resulting in one of the tightest feedback loops in the endocrine system. T4 is transformed into the only active hormone, triiodothyronine (T3), by a set of enzymes in peripheral tissues, the deiodinases. T3 regulates the transcription of large number of genes, with significant effects in almost every tissue. Several conditions can cause insufficient T4 production, with variable effects on many tissues, organs, and systems. Besides by history and physical exam, thyroid underactivity is accurately diagnosed by reliable measurements of serum TSH, T4, and T3. Since the defect in thyroid underactivity is lack of T4 production, treatment consists in the administration of supplemental T4, a safe, inexpensive, and effective product. Areas of uncertainty remain. The bioavailability of oral T4 is less than perfect in most and utterly insufficient in a few cases. Processes regulating the local production of T3, which could have significant impact on physiology and disease, remain poorly understood at the clinical level, due to the difficult access to thyroid hormone levels in individual tissues.] http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png

A Case-Based Guide to Clinical EndocrinologyIntroduction

Editors: Davies, Terry F.
Barbesino, Giuseppe
A Case-Based Guide to Clinical Endocrinology — Jan 4, 2022
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Publisher
Springer International Publishing
Copyright
© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2022
ISBN
978-3-030-84366-3
Pages
83 –86
DOI
10.1007/978-3-030-84367-0_9
Publisher site
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Abstract

[The thyroid is a highly specialized endocrine gland devoted to the production of thyroid hormones through several enzymatic steps. The thyroid hormones are iodinated derivatives of tyrosine and effect their functions through the interaction with nuclear receptor found in almost every human tissue. The thyroid mostly produces thyroxine, or tetraiodothyronine (T4), an inactive prohormone. The T4 production by the thyroid gland is almost only regulated by the pituitary hormone thyrotropin (TSH), which is in turn also almost only regulated by T4 levels, resulting in one of the tightest feedback loops in the endocrine system. T4 is transformed into the only active hormone, triiodothyronine (T3), by a set of enzymes in peripheral tissues, the deiodinases. T3 regulates the transcription of large number of genes, with significant effects in almost every tissue. Several conditions can cause insufficient T4 production, with variable effects on many tissues, organs, and systems. Besides by history and physical exam, thyroid underactivity is accurately diagnosed by reliable measurements of serum TSH, T4, and T3. Since the defect in thyroid underactivity is lack of T4 production, treatment consists in the administration of supplemental T4, a safe, inexpensive, and effective product. Areas of uncertainty remain. The bioavailability of oral T4 is less than perfect in most and utterly insufficient in a few cases. Processes regulating the local production of T3, which could have significant impact on physiology and disease, remain poorly understood at the clinical level, due to the difficult access to thyroid hormone levels in individual tissues.]

Published: Jan 4, 2022

Keywords: Thyroid; Hormones; Thyroxine; Triiodothyronine; Hypothyroidism

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