According to the International Headache Society, around 30 percent of people with an underactive thyroid gland (hypothyroidism) will have a history of headaches. Though the causes for this are poorly understood, we know that women are disproportionately affected and that the pain is usually unilateral (one-sided), pulsing, and often accompanied by nausea or vomiting. Moreover, half will have had a history of migraines prior to their diagnosis. The severity of the symptoms tends to rise and fall in tandem with the severity of the disease.

Headaches and Thyroid Function

Hypothyroidism, by definition, is characterized by the inadequate production of thyroid hormones needed to regulate metabolism—the conversion of calories and oxygen to energy so that the body has the fuel it needs to function normally.

When thyroid hormones are depleted, they can trigger a cascade of symptoms that affect metabolism (giving rise to weight gain and fatigue), brain function (manifesting with depression and cognitive impairment), and hormonal regulation (resulting in mood swings, irregular menstruation, and hair loss). One of the common symptoms of hypothyroidism is a headache.

While it would be reasonable to assume that hypothyroidism "causes" headaches, it is still unclear whether hypothyroidism if the cause or consequence of headaches, or if it only tangentially linked. The evidence is largely split.

Men vs. Women

Statistically speaking, women are three times as likely to experience migraines than men (18 percent versus 6 percent, respectively, according to research from John Hopkins University). Within this population of women, around 55 percent of migraine events are related to menstrual periods.

Similarly, women are 18 times more likely to have hypothyroidism than men, according to the Society for Endocrinology.

While this may suggest that migraines are simply a consequence of hormonal fluctuations during menstruation, it is important to note that the average age of onset of hypothyroidism in American women is 51. This is the time during which women will undergo (or have undergone) menopause and begin to experience an alleviation—rather than an increase—of migraine symptoms.

The fact that migraines can persist well after menopause substantiates hypothyroidism as a key contributing factor to migraine risk.

Are Headaches a Hypothyroidism Risk Factor?

Some researchers have inferred that a history of headaches and migraines may, in fact, predispose a person to hypothyroidism.

According to a study published in the journal Headache, among 8,412 people medically monitored over a 20-year period, those with pre-existing headache disorders had a 21 percent increased risk of new-onset hypothyroidism compared to people with no history of headaches.

Compared to the general population, people with a history of migraines specifically (as opposed to tension-type headaches) have a 41 percent increased risk of new-onset hypothyroidism.

What makes the study interesting is that the participants' thyroid functions were measured every three years during the 20-year period and that anyone with a prior history of thyroid disease or an abnormal thyroid reading at the start of the study was excluded.

While this in no way suggests that headaches are the "cause" of hypothyroidism, it does infer that a history of headaches may place you at greater risk of hypothyroidism.

Headaches and Thyroid Treatment

While thyroid hormone replacement therapy, most typically in the form of levothyroxine, can help minimize hypothyroid symptoms, some people will still experience recurrent headaches even after treatment. Again, whether or not the headaches are related to thyroid disease remains unclear.

In most cases, people with migraines and subclinical hypothyroidism (hypothyroidism with no observable symptoms) will see an improvement in headache symptoms after being placed on levothyroxine.

According to research presented at the Congress of the European Academy of Neurology in 2017, 45 people with subclinical hypothyroidism and migraines without aura experienced a drop in migraine incidence—from an average of 14.68 attacks per month to 1.86 attacks per month—after being placed on levothyroxine therapy.

It is not certain whether the same benefits would be afforded to people with overt (symptomatic) hypothyroidism.

It is also important to note that headache is a common side effect of levothyroxine use. In people with moderate to severe hypothyroidism, who would inherently require higher doses, the drug may, in fact, trigger headaches or worsen existing symptoms.

A Word From Verywell

It is not rare for people with hypothyroidism to have a headache disorder. While levothyroxine may help alleviate recurrent symptoms, particularly in people with subclinical or mild hypothyroidism, the results can vary from person to person.

In some cases, the symptoms won't improve, especially if you are experiencing a migraine or a tension-type headache. It is even possible that levothyroxine can make things worse.

In such cases, your headache or migraine would need to be diagnosed and treated as a distinct disorder. This may involve blood tests, imaging studies, and such treatment options as over-the-counter pain relievers, triptans, and ergot medications.

Migraine Headaches and Thyroid Disease