Background: A number of recent advances in our understanding of thyroid physiology may shed light on why some patients feel unwell while taking levothyroxine monotherapy. The purpose of this task force was to review the goals of levothyroxine therapy, the optimal prescription of conventional levothyroxine therapy, the sources of dissatisfaction with levothyroxine therapy, the evidence on treatment alternatives, and the relevant knowledge gaps. We wished to determine whether there are sufficient new data generated by well-designed studies to provide reason to pursue such therapies and change the current standard of care. This document is intended to inform clinical decision-making on thyroid hormone replacement therapy; it is not a replacement for individualized clinical judgment. Methods: Task force members identified 24 questions relevant to the treatment of hypothyroidism. The clinical literature relating to each question was then reviewed. Clinical reviews were supplemented, when relevant, with related...

Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement

Before marketing a new drug, the manufacturer almost never tests the product in pregnant women to determine its effects on the fetus. Consequently, most drugs are not labeled for use during pregnancy. Typically, descriptions of drugs that appear in the Physicians' Desk Reference and similar sources contain statements such as, “Use in pregnancy is not recommended unless the potential benefits justify the potential risks to the fetus.” Since the risk has been adequately established for only a few drugs, physicians caring for pregnant women have very little information to help them decide whether the potential benefits to the mother outweigh . . .

Drugs in Pregnancy

Testing of thyroid function is common in clinical practice. Many patients who are tested, including those who have or are receiving treatment for thyroid disease, take medications that may affect thyroid function. Therefore, the possible effect of these drugs both on the results of thyroid-function tests and on the effectiveness of treatment must always be considered in decisions regarding patient care. The pathways of thyroid hormone synthesis, secretion, transport in the circulation, and metabolism offer numerous targets for drug interaction (Figure 1 and Figure 2). Normal thyroid secretion depends on thyrotropin (TSH). Secretion of TSH is, in turn, inhibited by thyroid hormones . . .

https://www.nejm.org/doi/pdf/10.1056/NEJM199512213332507?listPDF=true

Drugs and Thyroid Function

Purpose: To review the indications for and the proper monitoring of levothyroxine therapy in patients with thyroid disease. Data Sources: Relevant English language articles published from 1966 to 1...

Levothyroxine Therapy in Patients with Thyroid Disease

J. Larry Jameson Anthony P. Weetman The thyroid gland produces two related hormones, thyroxine (T4) and tr i iodothyronine (T3) (Fig. 320-1). Acting through nuclear receptors, these hormones play a crit ical role in cell differentiation during development and help maintain thermogenic and metabolic homeostasis in the adult. Disorders of the thyroid gland result primari ly from autoimmune processes that either stimulate the overproduction of thyroid hormones ( thyrotoxicosis) or cause glandular destruction and hormone deficiency (hypothyroidism). In addit ion, benign nodules and various forms of thyroid cancer are relatively common and amenable to detection by physical examination.

Disorders of the Thyroid Gland

▪Objective:To determine whether simultaneous ingestion of ferrous sulfate and thyroxine reduces the efficacy of thyroid hormone in patients with primary hypothyroidism. ▪Design:Uncontrolle...

Ferrous Sulfate Reduces Thyroxine Efficacy in Patients with Hypothyroidism

Background Acute decreases in intravascular volume are associated with increases in lipid levels. Furosemide causes acute changes in intravascular volume during prolonged therapy but is thought to have little effect on lipid levels. Methods To determine if there are daily acute rises in lipid and lipoprotein levels associated with changes in intravascular volume during long-term furosemide ingestion therapy, we performed a randomized, double-blind, placebo-controlled crossover study in 10 patients. Results In the 8 hours after furosemide ingestion there were increases in levels of plasma cholesterol (10.1%; P =.001), high-density lipoprotein cholesterol (9.0%; P =.006), and apolipoprotein B (9.8%; P =.003). The increases in levels of triglycerides (11.5%; P =.17) and apolipoprotein A-1 (13.3%; P =.051) were of similar magnitude but more variable and did not achieve statistical significance. There was no substantial change in the total cholesterol–high-density lipoprotein cholesterol ratio (0.6%; 95% CI,−0.74% to 8.6%; P =.88). Conclusion This study indicates that there are acute increases in lipid levels after furosemide ingestion during prolonged therapy, which could affect the interpretation of lipid levels and cardiovascular risk in patients.

https://jamanetwork.com/journals/jamainternalmedicine/articlepdf/208030/ioi70895.pdf

Helga Stalts

Papers

Ferrous Sulfate Reduces Thyroxine Efficacy in Patients with Hypothyroidism

Fluctuations in Blood Lipid Levels During Furosemide Therapy: A Randomized, Double-blind, Placebo-Controlled Crossover Study