Improving lab diagnostics for patients with hypothyroidism using levothyroxine

Is this trial a fit for you?

A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.

What this trial studies

This observational study aims to enhance laboratory diagnostics for hypothyroid patients undergoing treatment with levothyroxine (L-T4). It focuses on understanding the relationship between serum thyroid-stimulating hormone (TSH) and free T4 (fT4) levels in patients with various forms of hypothyroidism. Participants will undergo a single blood draw and complete a questionnaire to gather data on their thyroid hormone status and treatment efficacy. The study seeks to clarify whether current diagnostic measures accurately reflect thyroid hormone levels in patients receiving L-T4 therapy.

Why it matters

Who can join: the full rules

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

Where it's running

• Amsterdam UMC
  Amsterdam, North Holland, Netherlands Recruiting

Study contacts

• Principal investigator: Annemieke C Heijboer, Prof. dr. — Amsterdam UMC, VU Amsterdam and UvA, Endocrine Laboratory, Department of Laboratory Medicine
• Study coordinator: Heijboer
• Email: a.heijboer@amsterdamumc.nl
• Phone: +31205665940

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How to take part

1. Review the eligibility criteria above with your treating physician.
2. Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
3. Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.