Your Free T4 Level

What Causes Abnormal Free T4 Levels?

Abnormal free T4 levels can have various causes, just like most other symptoms.  Finding the true cause means ruling out or confirming each possibility – in other words, diagnosis.

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Diagnosis is usually a complex process due to the sheer number of possible causes and related symptoms.  In order to diagnose abnormal free T4 levels, we could:

  • Research the topic
  • Find a doctor with the time
  • Use a diagnostic computer system.
The process is the same, whichever method is used.

Step 1: List all Possible Causes

We begin by identifying the disease conditions which have "abnormal free T4 levels" as a symptom.  Here are two possibilities:
  • Hyperthyroidism
  • Hypothyroidism

Step 2: Build a Symptom Checklist

We then identify all possible symptoms and risk factors of each possible cause, and check the ones that apply:
occasional 'chills'
joint pain/swelling/stiffness
poor tolerance of heat
difficulty losing weight
very strong appetite
high iodine consumption
animal-derived thyroid hormone use
having low-normal TT4 level
history of hyperthyroidism
premenstrual bloating/weight gain
elevated lymphocyte count
fatigue after slight exertion
... and more than 60 others

Step 3: Rule Out or Confirm each Possible Cause

A differential diagnosis of your symptoms and risk factors finds the likely cause of abnormal free T4 levels:
Cause Probability Status
Hypothyroidism 99% Confirm
Hyperthyroidism 58% Possible
* This is a simple example to illustrate the process

Arriving at a Correct Diagnosis

The Analyst™ is our online diagnosis tool that learns all about you through a straightforward process of multi-level questioning, providing diagnosis at the end.

If you indicate having had recent lab tests, The Analyst™ will ask further questions including this one:
T4 (Free). Unit: ng/dL [pmol/L]
Possible responses:
→ Don't know
→ Under 0.4 [5] (very low)
→ 0.4 to 0.8 [5-10] (low)
→ 0.9 to 2.0 [11-26] (normal)
→ Over 2.0 [26] (elevated)
Based on your response to this question, which may indicate very low free T4, low free T4, normal free T4 or elevated free T4, The Analyst™ will consider possibilities such as:
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