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Poor acid secretion impairs thyroxine absorption.(Clinical Rounds)
Patients with multinodular goiter required a thyroxine dosage increase of 22%-34% if they had impaired secretion of stomach acids, results from a large controlled study demonstrated.
The finding suggests that "normal gastric acid secretion is important for the subsequent intestinal absorption of thyroxine," wrote the researchers, who were led by Dr. Marco Centanni of the department of experimental medicine and pathology at La Sapienza University, Rome.
"Although the clinical importance of these findings is fairly clear, the mechanism by which intestinal absorption of thyroxine is impaired in patients with hypochlorhydria is unknown. We may only speculate that oral thyroxine is administered as sodium salt that is less lipophilic than the native hormone, which enters target cells both through passive diffusion and in a carrier-mediated, inhibitable way. In this respect, achlorhydria due to atrophic gastritis, the production of ammonia, or both, which are characteristic of [Helicobacter] pylori infection, may alter the ionization status and the conformational characteristics of the thyroxine molecule and thus the efficiency of intestinal absorption of the hormone."
Dr. Centanni and his associates studied 248 patients with nontoxic multinodular goiter who were seen at a referral center for thyroid disease between 1999 and 2004. Of the 248 patients, 53 also had H. pylori-related gastritis and 60 had atrophic gastritis of the body of the stomach (31 with evidence of H. Pylori infection and 29 without such evidence).
The remaining 135 patients had no gastric disorders and served as the reference group (N. Engl. J. Med. 2006;354:1787-95).
All patients received an initial thyroxine dosage of 50 [micro]g/day and were followed for at least 30 months. The researchers evaluated the thyroid-pituitary axis every 4 months and, if needed, increased the thyroxine dosage until a low serum thyrotropin level was achieved on at least two consecutive measurements. The serum ...
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Source: Parle JV, et al. Lancet. 2001; 358:861-865. SUBCLINICAL HYPERTHYROIDISM (SCH) is defined as a subnormal TSH level accompanied by normal levels of T4 and T3; as is implied in the name designation, persons must also be free of symptoms of hyperthyroidism. The pathologic consequences (or lack
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...food impairing its absorption. The serum thyrotropin concentration is the therapeutic...administration in relationship to food on serum thyrotropin levels. Participants were randomized...levothyroxine was taken with breakfast, the serum thyrotropin concentration was significantly ...
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- Magazine article from: Internal Medicine News Macready, Norra September 15, 2001 700+ words
...postmenopausal women on thyroxine, serum thyrotropin levels should be measured after about...correlated inversely with an increase in serum thyrotropin concentrations. The changes in serum thyrotropin concentrations were clinically important...
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- Magazine article from: OB GYN News MacReady, Norra August 15, 2001 700+ words
...thyroxine should measure their patients' serum thyrotropin levels approximately 12 weeks after...correlated inversely with an increase in serum thyrotropin concentrations. The changes in serum thyrotropin concentrations were clinically important...
- Estrogen Replacement Therapy May Exacerbate Hypothyroidism.(Brief Article)
- Magazine article from: Family Practice News Macready, Norra September 1, 2001 700+ words
...thyroxine should measure their patients' serum thyrotropin levels approximately 12 weeks after...correlated inversely with an increase in serum thyrotropin levels. The changes in serum thyrotropin concentrations were clinically important...
- Little consensus on gestational thyroid screening.(Metabolic Disorders)
- Magazine article from: Family Practice News Wendling, Patrice January 1, 2007 700+ words
...diagnosis of pregnancy. The preconception thyroxine dosage should be adjusted to reach a serum...higher than 2.5 microIU/L. The thyroxine dosage usually needs to be incremented by...undisclosed prolonged hypothyroidism. Thyroxine dosage should be titrated to rapidly reach...
- Thyroid Guidelines.
- Newspaper article from: Psychiatric Medicine in Primary Care November 1, 2000 700+ words
...screened for thyroid dysfunction by the measurement of serum thyrotropin concentration, beginning at age 35 years and every five...laboratory screening, typically via the measurement of serum thyrotropin concentration, is warranted because hypothyroidism and...
- Pseudo-central hypothyroidism. (Case Report).
- Magazine article from: Southern Medical Journal Basaria, Shehzad Altman, Kristina Braga-Basaria, Milena February 1, 2003 700+ words
...thyrotoxic symptoms, and the dose should be titrated to keep serum thyrotropin levels within the normal range. In addition to a careful...PA, Belanger AJ, Baker E, Bacharach P, et al. Low serum thyrotropin concentrations as a risk factor for atrial fibrillation...
