No Treatment Needed – Your Patient Has Normal Thyroid Function
Your patient's thyroid function is completely normal and requires no intervention. With a TSH of 0.373 mIU/L (within the reference range of 0.45-4.5 mIU/L, though just slightly below in some lab ranges) and a free T4 of 1.24 ng/dL (solidly normal), she has euthyroid status despite her goiter 1.
Understanding the Clinical Picture
The presence of a goiter does not automatically indicate thyroid dysfunction. Many patients with longstanding thyroid disease, particularly those with Hashimoto's thyroiditis or multinodular goiter, maintain normal thyroid function for years or indefinitely 1, 2. Your patient's current biochemical profile demonstrates:
- TSH at 0.373 mIU/L: This falls at the lower end of normal but does NOT indicate hyperthyroidism requiring treatment, as persons with TSH between 0.1-0.45 mIU/L are unlikely to progress to overt hyperthyroidism 1
- Free T4 at 1.24 ng/dL: This is solidly within the normal reference range, confirming adequate thyroid hormone production 1
- The combination definitively excludes both overt and subclinical thyroid dysfunction 1
What This Means for Management
Continue observation without initiating thyroid hormone therapy. Starting levothyroxine in a euthyroid patient would create iatrogenic hyperthyroidism, increasing risks for atrial fibrillation (especially concerning given her age and any cardiac history), osteoporosis, fractures, and cardiovascular complications 1, 2.
Monitoring Strategy
Recheck thyroid function tests in 6-12 months, or sooner if symptoms develop 1. Specifically monitor for:
- Symptoms of hypothyroidism: fatigue, weight gain, cold intolerance, constipation, cognitive changes 2
- Symptoms of hyperthyroidism: palpitations, tremor, heat intolerance, unintentional weight loss, anxiety 3
- Changes in goiter size or development of compressive symptoms 4
If TSH remains in the 0.3-0.45 range on repeat testing with normal free T4, continue annual monitoring 1. This low-normal TSH may simply represent her individual set point and does not warrant treatment.
Critical Pitfalls to Avoid
Do not treat based on the presence of goiter alone. Approximately 25% of patients inappropriately receive levothyroxine when not indicated, leading to iatrogenic complications 1. The goiter should be evaluated by her endocrinologist for:
- Structural concerns (compressive symptoms, malignancy risk)
- Underlying etiology (autoimmune disease, multinodular goiter)
- Need for thyroid antibody testing if not previously done 1
Do not assume a single borderline TSH value indicates disease. TSH secretion is highly variable and sensitive to acute illness, medications, time of day, and physiological factors 1. A TSH of 0.373 mIU/L with normal free T4 does not meet criteria for subclinical hyperthyroidism (which requires TSH <0.1 mIU/L with normal thyroid hormones) 1.
When to Reconsider
Repeat thyroid function testing is indicated if:
- New symptoms develop suggesting thyroid dysfunction 1
- The patient develops acute illness, as nonthyroidal illness can transiently affect thyroid tests 5
- She starts new medications that affect thyroid function (amiodarone, lithium, immune checkpoint inhibitors) 3, 2
- The goiter enlarges or causes compressive symptoms 4
For now, reassure your patient that her thyroid hormone levels are normal and no treatment is needed. Coordinate with her endocrinologist regarding the structural management of her goiter, but from a biochemical standpoint, she requires only surveillance 1.