💬In plain words
What the trial is, and whether it could suit you
Hypothyroidism is a thyroid disorder and one of the most common endocrine disorders. Hypothyroidism can have multiple causes; most patients suffer from primary autoimmune hypothyroidism (Hashimoto's disease), but also central hypothyroidism, hypothyroidism after total thyroidectomy due to thyroid carcinoma, or hypothyroidism due to therapy of Graves' disease occur. Most patients with hypothyroidism are treated with levothyroxine (L-T4) to supplement the lack of thyroxine (T4) produced by their own thyroid. Serum thyroid-stimulating hormone (TSH) and/or free T4 (fT4) are currently measured to assess the efficacy of this therapy and to establish euthyroidism. It is known that fT4 concentrations in patients using L-T4 can be above the upper limit of the reference interval, while their TSH is not (completely) suppressed. This raises the question whether fT4 is an accurate reflection of thyro
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📋 Eligibility rules (as published)
Inclusion Criteria:
In order to be eligible to participate in this study, a hypothyroid subject must meet all of the following criteria:
* Ability to provide informed consent
* Ability to speak and understand Dutch or English
* Intake of a stable dosage of levothyroxine, meaning the dosage of levothyroxine must not be changed during the appointment at the outpatient clinic
* Diagnosis of one these forms of hypothyroidism
* Patients with primary hypothyroidism: euthyroid based on TSH according to physician
* Patients with hypothyroidism after a total thyroidectomy due to thyroid carcinoma (therefore athyroid): on target TSH according to physician (target TSH depending on stage/severity of carcinoma)
* Patients using L-T4 due to therapy of Graves' disease: euthyroid based on TSH according to physician (TSH cannot be suppressed, namely TSH within reference interval of 0,5-5,0 mU/L)
* Patients with central hypothyroidism: euthyroid based on fT4 according to physician (common is fT4 in the upper limit, reference interval is 12-22 pmol/L)
In order to be eligible to participate in this study, a healthy control subject must meet all of the following criteria:
* Ability to provide informed consent;
* Ability to speak and understand Dutch or English
* Consider themselves healthy
Exclusion Criteria:
A potential hypothyroid subject who meets any of the following criteria will be excluded from participation in this study:
* Not euthyroid according to physician
* Pregnancy
* Patients using L-T4 due to therapy of Graves' disease: if TSH is still suppressed
* Any of the following medication
* Liothyronine (Cytomel)
* Iodide
* Oral contraceptives
* Active treatment of malignancy (other than thyroid carcinoma)
A potential healthy control subject who meets any of the following criteria will be excluded from participation in this study:
* Pregnancy
* Any of the following medication
* Thyroid medication (a.o. levothyroxine, thiamazol, PTU)
* Lithium
* Amiodarone
* Propranolol
* Iodide
* Glucocorticoids
* Oral contraceptives
* Heparin
* Growth hormone
* Active treatment of malignancy
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