What Is the Link Between Migraine and Hypothyroidism? A Systematic Literature Review.

: Hypothyroidism is defined as a deficiency of thyroid hormones and is further classified into primary, secondary, and tertiary types, based on the root cause of the deficiency. Migraine is a primary headache disorder, characterized by unilateral, pulsating pain, lasting from 4 to 72 h, accompanied by symptoms such as photophobia, phonophobia, nausea, and emesis and sometimes preceded by specific aura phenomena. Both diseases are more prevalent in women than in men. While the primary focus of this systematic review was on the relationship between hypothyroidism and migraine, we also included relevant data on headaches in general when they provided valuable context or mechanistic insight. : This systematic review aimed to summarize the current knowledge about the relationship between migraine and hypothyroidism. The Preferred Reporting Items for Systematic Reviews (PRISMA) guidelines were applied. Screening of two databases led to including 29 relevant studies in the review. : Studies demonstrated that migraine and disturbed thyroid function may influence one another. The positive correlation between migraine and hypothyroidism, mainly Hashimoto's disease, was presented in several studies. Moreover, some research identified this correlation in pediatric populations. Finally, the effects of levothyroxine use, a treatment applied in hypothyroidism, on migraine course were presented. : A better understanding of the correlation between migraine and hypothyroidism may lead to an increase in the understanding of the pathogenesis of both disorders and positively impact clinical practice.