Thyroid testing: Hits and misses

The thyroid gland may be small, but its impact on the human body is extensive. Positioned at the front of the neck, this butterfly-shaped gland produces hormones that influence metabolism, heart rate, digestion, mood, fertility, and temperature regulation. When thyroid function shifts even slightly, the effects can be felt across multiple organ systems.

Despite the widespread availability of blood tests and growing public awareness, thyroid disorders remain among the most commonly misdiagnosed endocrine conditions. Endocrinologists point out that this is not due to a lack of testing, but often because thyroid function is dynamic, influenced by medication adherence, testing practices, autoimmune activity, and timing.

Hypo or hyper

Hypothyroidism occurs when the thyroid does not produce adequate hormones. Patients commonly experience fatigue, weight gain, cold intolerance, dry skin, constipation, hair thinning, menstrual irregularities, and low mood. The most frequent cause is Hashimoto’s thyroiditis, an autoimmune condition in which antibodies gradually damage thyroid tissue.

Hyperthyroidism, on the other hand, results from excess thyroid hormone production. Symptoms include unintentional weight loss, palpitations, tremors, heat intolerance, anxiety, increased sweating, and sleep disturbance. Graves’ disease is the most common autoimmune cause.

While hypothyroidism and hyperthyroidism appear distinct, endocrinologists emphasise that real-world presentations are rarely textbook. Many symptoms overlap with stress, mental health disorders, ageing, or lifestyle-related fatigue, leading to frequent diagnostic confusion.

The overlooked middle

One of the biggest reasons for thyroid misdiagnosis lies in the assumption that thyroid tests are static and absolute. In reality, thyroid hormones fluctuate, especially in autoimmune thyroid disease. Patients with thyroid antibodies may move between normal, borderline, and abnormal values over weeks or months. Testing during one of these transitional phases may produce misleading reassurance or unnecessary alarm.

This is particularly relevant in individuals who have:

 Positive thyroid antibodies but normal hormone levels

 Early or evolving autoimmune disease

 Recently started or inconsistently taken thyroid medication

Endocrinologists often see patients tested too frequently, sometimes every few weeks, without allowing enough time for the body to reach hormonal equilibrium. Thyroid hormone levels, especially TSH, take several weeks to stabilise after any dose change. Frequent testing can create the illusion of instability where none truly exists.

Testing errors, lab variability

Another underappreciated issue is laboratory variability. Not all labs follow uniform calibration protocols, and reference ranges may differ between centres. A patient testing at different laboratories may see fluctuating reports despite no true change in thyroid status.

Timing matters

When blood samples are drawn from patients in certain scenarios, they may show misleading results.

These scenarios include:

 Missed doses

 Taken medication incorrectly

 Changed brands

 Tested too soon after starting or stopping treatment

The situation becomes even more complex when patients change doctors frequently, resulting in different interpretations of the same data without longitudinal context.

Single test not helpful

Many diagnoses are based solely on TSH levels. While TSH is a sensitive screening marker, it does not always reflect the full picture. Early disease, autoimmune activity, and central thyroid disorders may be missed if free T4, free T3, and antibody testing are not considered when clinically appropriate. Endocrinologists stress that thyroid disease cannot be reduced to a single number. Symptoms, trends over time, medication history, antibody status, and clinical judgement must all be integrated.

Why accurate diagnosis matters

Untreated hypothyroidism can worsen cholesterol levels, increase cardiovascular risk, impair fertility, and significantly affect quality of life. Undiagnosed hyperthyroidism raises the risk of arrhythmias, bone loss, muscle wasting, and emotional instability.

Equally important is the psychological impact. Many patients feel dismissed when symptoms persist despite “normal” reports. This disconnect between lived experience and laboratory values is a major source of frustration and delayed care.

An endocrinologist-led approach

Endocrinologists advocate for a nuanced, patient-specific approach:

 Testing at appropriate intervals

 Ensuring medication adherence before testing

 Using the same laboratory when possible

 Interpreting results in clinical context

 Recognising autoimmune thyroid disease as a spectrum, not a fixed state

Thyroid health exists on a continuum rather than a normal-or-abnormal scale. Thyroid disorders are common, but they are rarely simple. Misdiagnosis often arises not from lack of testing, but from over-testing, poor timing, inconsistent medication use, laboratory variability, and failure to recognise fluctuating autoimmune disease. Understanding these nuances helps patients and doctors move beyond isolated numbers and towards more accurate, compassionate, and effective thyroid care.

(The writer is a consultant - endocrinologist diabetes and thyroid at a Bengaluru hospital.)