In this case, we have a 35-year-old female patient referred for neurological clinical care due to the development of a chronic headache that began 8 months ago. She denied a similar headache previously. She reported daily frequency and progressive worsening in intensity. In addition to the pain, she reported nonspecific symptoms (including fatigue, sleep disturbance, mood dysfunction, constipation, cold intolerance, recent weight gain, dry skin, and hair loss), with progressive worsening. Complementary exams showed hypothyroidism (elevated thyroid-stimulating hormone [TSH], low fT4, positive anti-thyroid peroxidase (anti-TPO) antibody and other exams, including magnetic resonance imaging (MRI), were normal. The patient was treated with levothyroxine, with dose adjustment according to TSH levels, with clinical improvement. Although its pathophysiology remains unknown, there is evidence that it is mainly due to serotonergic dysfunction in hypothyroidism. Diagnosis is based on laboratory tests (TSH and fT4), in addition to excluding differential diagnoses of other headaches. Treatment is with hormone replacement therapy using oral levothyroxine. Clinically, it may present with different characteristics. Therefore, we suggest that TSH and fT4 levels be measured in all investigations of secondary headache, considering not only the diagnosis of headache attributed to hypothyroidism (HAH) but also the bidirectional relationship between hypothyroidism and other headaches.