When Headache Persists Despite “Normal” Findings

Chronic tension-type headache and migraine are among the most common and disabling neurological complaints. Despite appropriate diagnosis and treatment, many patients continue to experience persistent or refractory symptoms.

In otolaryngology practice, patients with chronic frontal, facial, or periorbital headache are frequently referred to exclude sinonasal or otologic disease. When ENT examination and imaging are normal, the underlying cause often remains unclear.

A normal TSH does not exclude thyroid-related headache; it often excludes further investigation.

One frequently overlooked contributor is autoimmune thyroid disease, particularly in patients who appear euthyroid based on serum thyroid-stimulating hormone (TSH) alone.

Thyroid Autoimmunity Without Abnormal TSH

Thyroid dysfunction has long been associated with headache syndromes. While overt hypothyroidism is a recognized trigger, many patients with Hashimoto’s thyroiditis remain biochemically euthyroid yet experience neurological and systemic symptoms.

These patients commonly report chronic headache, fatigue, cold intolerance, cognitive slowing, and musculoskeletal discomfort. Such findings suggest impaired tissue-level thyroid hormone action, immune-mediated effects, or altered pain modulation not reflected by serum TSH values.

Low Basal Body Temperature as a Functional Marker

A consistent clinical finding in this patient population was low basal body temperature (BBT). Morning oral temperatures, measured upon waking, were persistently subnormal, typically ranging from 35.6–36.2°C (96.1–97.2°F).

Basal body temperature reflects tissue-level thyroid hormone action in a way serum TSH cannot.

Low BBT reflects reduced metabolic heat production and provides insight into functional thyroid status beyond laboratory reference ranges. Improvement in basal body temperature following thyroid-directed therapy closely paralleled improvement in headache frequency and intensity.

Recognizable Physical Signs in Hypothyroid Headache Patients

Careful physical examination revealed a distinct constellation of hypothyroid signs, often present despite normal laboratory results and frequently overlooked in routine evaluations.

The eyebrows, skin, hair, and hands often reveal hypothyroidism long before laboratory values do.

Common findings included thinning or loss of the outer third of the eyebrows (Hertoghe sign), diffuse scalp hair thinning, puffy or periorbital facial appearance, cold hands and feet, melasma or facial hyperpigmentation, and dry, cool, or pale skin.

These signs often preceded biochemical abnormalities and improved gradually with thyroid-directed treatment.

Thyroid Ultrasound: Seeing What Blood Tests Miss

All patients underwent high-resolution thyroid ultrasonography, which consistently revealed changes compatible with autoimmune thyroid disease.

Typical findings included diffuse hypoechogenicity, parenchymal inhomogeneity, pseudonodular patterns, increased Doppler vascularity, thyroid nodules, and gland enlargement or atrophy depending on disease stage.

Thyroid ultrasound frequently reveals autoimmune disease that blood tests miss.

Importantly, ultrasound abnormalities were observed even in patients with negative thyroid autoantibodies, supporting the existence of seronegative autoimmune thyroiditis.

Clinical Pearls: Evaluating Chronic Headache When TSH Is Normal

• Normal TSH does not exclude thyroid-related headache.
• Persistently low basal body temperature suggests impaired tissue-level thyroid hormone action.
• Physical signs such as Hertoghe sign, hair thinning, facial puffiness, cold extremities, and skin changes provide early diagnostic clues.
• Thyroid ultrasound may reveal autoimmune thyroid disease even when antibodies are negative.
• Thyroid-directed therapy may significantly improve headache frequency, intensity, and refractoriness.

Clinical Vignette 1: Refractory “Sinus Headache” With Normal TSH

A 42-year-old woman was referred for evaluation of chronic frontal and periorbital headache of more than five years’ duration. Multiple courses of antibiotics, nasal sprays, antihistamines, and migraine therapies had provided little relief. ENT examination and sinus imaging were normal, and serum TSH was within the reference range.

Physical examination revealed thinning of the outer third of the eyebrows, diffuse hair thinning, periorbital puffiness, dry skin, and cold hands. Morning basal body temperature averaged 36.0°C (96.8°F). Thyroid ultrasound demonstrated diffuse hypoechogenicity consistent with autoimmune thyroiditis, and anti-TPO antibodies were elevated.

After initiation and optimization of levothyroxine therapy, headache frequency and intensity decreased markedly within weeks. Basal body temperature increased toward normal, facial puffiness diminished, and energy improved.

These patients were not treatment-resistant—the diagnosis was.

Clinical Vignette 2: Migraine in a “Euthyroid” Patient With Seronegative Autoimmune Thyroiditis

A 36-year-old woman presented with chronic migraine despite preventive therapy. Neurologic imaging was unremarkable. Serum TSH, free T4, and thyroid antibodies were normal.

Physical examination revealed diffuse hair thinning, melasma, cold extremities, and puffy facial features. Morning basal body temperature was persistently low. Thyroid ultrasound demonstrated a pseudonodular pattern and diffuse hypoechogenicity consistent with autoimmune thyroiditis.

Following thyroid-directed therapy, migraine frequency and severity decreased substantially, basal body temperature improved, and associated systemic symptoms resolved.

Clinical Outcomes With Thyroid-Directed Therapy

Across patients, thyroid-directed treatment was associated with reduced headache frequency and intensity, improved response to standard headache therapies, improvement in cold intolerance and fatigue, gradual normalization of basal body temperature, and partial reversal of physical signs.

When thyroid function improves, headache frequency, intensity, and refractoriness often improve with it.

Conclusion

Chronic headache may be the presenting symptom of autoimmune thyroid disease, not a coincidental comorbidity.

Autoimmune thyroid disease may contribute to chronic tension-type headache and migraine even in patients with normal serum TSH levels. Reliance on circulating thyroid markers alone risks overlooking functionally hypothyroid states in which thyroid hormone availability at the tissue and cellular level is impaired.

Basal body temperature represents a direct functional expression of thyroid hormone action at the cellular level, particularly within the mitochondria. Thyroid hormones—especially triiodothyronine (T3)—are critical regulators of mitochondrial biogenesis, oxidative phosphorylation, and adenosine triphosphate (ATP) production. Adequate intracellular thyroid hormone signaling increases mitochondrial activity, ATP generation, and metabolic heat production. When thyroid hormone transport, conversion, receptor binding, or intracellular signaling is impaired—as may occur in autoimmune thyroid disease—mitochondrial energy production declines, resulting in reduced heat generation and persistently low basal body temperature.

In this context, low basal body temperature reflects intracellular or tissue-level hypothyroidism, even when serum TSH remains within reference ranges. Reduced mitochondrial ATP availability may impair neuronal energy metabolism, pain modulation, muscle function, and vascular regulation, providing a plausible mechanistic link between functional hypothyroidism and chronic headache syndromes.

Chronic headache may therefore represent a clinical manifestation of impaired cellular energy metabolism driven by autoimmune thyroid disease rather than a purely primary neurological disorder.

Incorporating assessment of basal body temperature, characteristic hypothyroid physical signs, thyroid autoimmunity, and thyroid ultrasonography into the evaluation of refractory headache allows clinicians to identify this intracellular hypothyroid state and initiate targeted thyroid-directed therapy, with the potential for meaningful and sustained symptom improvement.

The central role of thyroid hormone in regulating mitochondrial function, oxidative phosphorylation, and ATP-dependent thermogenesis has been well described in endocrine and metabolic literature, with reduced thyroid hormone signaling consistently associated with decreased mitochondrial energy production and lower metabolic heat generation.¹

Reference

1. Wiersinga WM. Paradigm shifts in thyroid hormone replacement therapies for hypothyroidism. Nat Rev Endocrinol. 2014;10(3):164–174.