While the presentation and underlying causes of headaches are diverse and poorly understood, the International Headache Society (IHS) broadly classifies headaches as either primary or secondary.
Primary headaches include symptom-based headaches with examples including migraine, tension-type headache, trigeminal autonomic cephalalgias and cluster headache, whereas
secondary headaches — or etiology-based headaches — are often related to a pre-existing condition, such as trauma or injury to the head and/or neck, cranial or cervical vascular disorder, substance use (eg, medication), infection, disrupted homeostasis, or psychiatric disorder.
The recently updated, third edition (beta version) of the International Classification of Headache Disorders (ICHD-3 Beta) provides a comprehensive update of the different types of headache, the criteria that distinguish them, and key considerations for diagnosis
The current nomenclature of headaches attributed to disorder of homeostasis includes headaches that resolve or significantly improve following treatment or spontaneous re-establishment of homeostasis.
According to the ICHD-3 Beta, headaches secondary to a disruption of homeostasis include those attributed to
- hypoxia and/or hypercapnia (ie, high altitude, diving, or sleep apnea),
- arterial hypertension,
- cardiac cephalalgia, and
- other factors affecting homeostasis.
Headaches caused by disorder of homeostasis (have a significant female preponderance with an estimated lifetime prevalence of approximately 22% of the general population based on limited population-based studies.
Although the underlying pathophysiology of homeostasis-related headaches is not yet clearly defined, the nervous and endocrine systems are thought to be involved through the maintenance of homeostasis. Therefore, dysfunction of the endocrine system may lead to various neurologic manifestations, including headaches
It thus appears that early and effective treatment of endocrine or hormonal imbalance can relieve neurologic symptoms associated with headaches
High altitude (or hypobaric hypoxia) headache affects approximately 80% of individuals who ascend to high altitude and is thought to be due to hypoxia-induced changes in cerebral blood flow
Hypoxia as a trigger for migraine attacks was demonstrated in a randomized, double-blind, sham-controlled study in which a state of hypoxia increased lactate in a specific region of the brain and cranial arteritis
Headache is common among individuals undergoing hemodialysis
The prevalence of headache attributed to hypothyroidism has been shown to be comparable among patients with either subclinical or overt hypothyroidism and with comparable improvement in headache when treated with levothyroxine.
An association between pain sensitivity, thyroid status, and alteration in serotonin level and regulation have been speculated as underlying pathologic mechanisms. The latter was demonstrated in rats in which diminished serotonin levels were observed after thyroidectomy.
While evidence is emerging linking headache with disorders of homeostasis, this is complicated by observations and studies that show persistence of headache despite re-establishment of homeostasis.
The obvious question that arises is whether an imbalance of homeostasis is one of several causes of the presenting headache. A study reported that despite treatment of hypothyroidism, 21% of patients continued to experience headache 12 months after treatment.
This seems to undermine the whole point of this article. It seems to be almost hidden at the very bottom of the text above the final Summary.
Summary and Clinical Applicability
An improved understanding of the link between headache and homeostasis might allow earlier diagnosis and better management or treatment of conditions that trigger imbalance in homeostasis, thereby circumventing the morbidity and mortality that can result from diagnostic and treatment delays.