The term subclinical hypothyroidism (SCH) was coined by Bastenie et al1 in 1967, and the entity has remained a subject of a heated debate among clinicians ever since. There appears to be agreement on the basic definition of SCH as the finding of a thyrotropin (TSH) level above the upper limit of the reference range in the presence of normal reference range levels of serum free thyroxine (FT4) and free triiodothyronine (FT3).2 The controversy relates in part to just what is the normal reference range for TSH level, specifically the upper limit of the range beyond which a diagnosis of hypothyroidism would obtain. That upper limit has been falling in recent years from values of 6.5 or 7.0 mIU/L down to 4.1 to 4.5 mIU/L in most laboratories. We have argued that the upper limit of the reference range will be yet lower when reference populations are corrected for underlying or occult thyroid disease, goiter, antithyroid antibodies, and a family history of thyroid disease. When this is done, the mean serum TSH ranges from 1.2 to 1.5 mIU/L and the upper limit for the 97.5th percentile is 2.5 mIU/L.3
Register and get free email Table of Contents alerts, saved searches, PowerPoint downloads, CME quizzes, and more
Subscribe for full-text access to content from 1998 forward and a host of useful features
Activate your current subscription (AMA members and current subscribers)
Purchase Online Access to this article for 24 hours
Thank you for submitting a comment on this article. It will be reviewed by JAMA Internal Medicine editors. You will be notified when your comment has been published. Comments should not exceed 500 words of text and 10 references.
Do not submit personal medical questions or information that could identify a specific patient, questions about a particular case, or general inquiries to an author. Only content that has not been published, posted, or submitted elsewhere should be submitted. By submitting this Comment, you and any coauthors transfer copyright to the journal if your Comment is posted.
* = Required Field
Disclosure of Any Conflicts of Interest*
Indicate all relevant conflicts of interest of each author below, including all relevant financial interests, activities, and relationships within the past 3 years including, but not limited to, employment, affiliation, grants or funding, consultancies, honoraria or payment, speakers’ bureaus, stock ownership or options, expert testimony, royalties, donation of medical equipment, or patents planned, pending, or issued. If all authors have none, check "No potential conflicts or relevant financial interests" in the box below. Please also indicate any funding received in support of this work. The information will be posted with your response.
Some tools below are only available to our subscribers or users with an online account.
Download citation file:
Web of Science® Times Cited: 5
Customize your page view by dragging & repositioning the boxes below.
More Listings atJAMACareerCenter.com >
and access these and other features:
Enter your username and email address. We'll send you a link to reset your password.
Enter your username and email address. We'll send instructions on how to reset your password to the email address we have on record.
Athens and Shibboleth are access management services that provide single sign-on to protected resources. They replace the multiple user names and passwords necessary to access subscription-based content with a single user name and password that can be entered once per session. It operates independently of a user's location or IP address. If your institution uses Athens or Shibboleth authentication, please contact your site administrator to receive your user name and password.