Brain fog, fatigue and cognitive problems in hypothyroidism

tired man touching neck, thyroid

A University of Chicago research team investigated reports of persistent brain fog in people with hypothyroidism, even with thyroid hormone replacement therapy, and found that it was also frequently linked to fatigue and cognitive symptoms. The results were published in endocrine practice.

The study analyzed survey responses from 5,170 people with hypothyroidism (95.9% female) who responded to an online survey conducted between September 15 and October 26, 2020. Participants were asked to identify the cause of their hypothyroidism if known, such as Hashimoto’s thyroiditis, thyroid surgery, radioactive iodine treatment or a combination of these. The 10-question survey asked patients about the cause, frequency, duration (including time of day), and definition of brain fog. Patients rated the frequency of other symptoms coinciding with the brain fog and the extent to which the brain fog negatively interfered with function. Additionally, patients described in their own words what they perceived to be improving or worsening their brain fog.

Following text data analysis of survey responses, investigators calculated that 2409 (46.6%) people reported brain fog prior to their diagnosis of hypothyroidism and 4096 (79.2%) experienced brain fog. brain fog frequently or all the time. More than half of the respondents (56.4%) said their brain fog lasted all day, while the rest reported less brain fog in the evening. Fatigue and forgetfulness have been commonly reported with brain fog.

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Over 95% of respondents cited fatigue, forgetfulness, drowsiness, and lack of concentration as the most common symptoms coinciding with brain fog, saying these symptoms typically negatively impact their lives. Lifestyle modifications that improved brain fog and associated symptoms included rest (51.7%), thyroid hormone replacement dosage adjustments (28.3%), and exercise (10.4 %). Liothyronine (LT3) supplementation improved brain fog symptoms more than desiccated thyroid extract (8.3% vs. 4.0%).

The authors of the study noted several limitations. The participants were a non-random sample of people who reported having hypothyroidism with brain fog symptoms and who had regular access to hypothyroidism-related websites where the survey was posted, which the investigators considered a form of selection bias. The survey was also designed to be low-key to encourage maximum participation, so it did not include medical information to confirm the diagnosis of hypothyroidism.

In addition to hypothyroidism, chronic fatigue syndrome, chemotherapy, postural orthostatic tachycardia syndrome, and aging can contribute to brain fog and related symptoms, researchers say. About 46% of survey respondents claimed to have experienced brain fog prior to a diagnosis of hypothyroidism, implying that other conditions may have influenced the symptoms.

“The present study characterizes brain fog from the perspective of patients with hypothyroidism as a spectrum of symptoms that represent a significant cognitive and functional burden in daily life,” the authors said. “Exploring…new areas of patient concern may provide a new avenue for addressing the hypothyroid patient experience, in addition to the traditional approach to thyroid-specific symptoms,” they concluded.

Disclosure: One study author declared affiliations with private industry. Please see the original citation for a full list of author disclosures.


Ettleson MD, Raine A, Batistuzzo A, et al. Brain fog in hypothyroidism: understanding the patient’s perspective. Practice Endocr. Uploaded December 8, 2021. doi:10.1016/j.eprac.2021.12.003