Can hypothyroidism cause depression?

From the Guidelines

Hypothyroidism can indeed cause depression, as the lack of thyroid hormones can lead to various psychological symptoms, including depression, anxiety, and cognitive difficulties. This is because thyroid hormones play a crucial role in regulating brain function and metabolism, as noted in a systematic review on the hypothalamic-pituitary-thyroid (HPT) axis functioning in anxiety disorders 1. The review highlights that patients with overt hypothyroidism exhibit symptoms that overlap with those of major depression, and some patients with depressive disorders seem to be characterized by subclinical forms of hypothyroidism.

Some key points to consider:

• Thyroid hormones are essential for brain function, and their deficiency can lead to depressive symptoms, as seen in patients with overt hypothyroidism 1.
• The depression associated with hypothyroidism often improves when the underlying thyroid condition is treated with thyroid hormone replacement therapy, typically levothyroxine (synthetic T4) at doses determined by a healthcare provider based on blood tests.
• The standard approach involves starting at a low dose (usually 25-50 mcg daily) and gradually increasing until thyroid levels normalize, which can help alleviate depressive symptoms.
• If you're experiencing depression and have risk factors for thyroid disease, it's essential to have your thyroid function tested, as treating the underlying hypothyroidism may significantly improve mood symptoms, as suggested by the systematic review on HPT axis functioning in anxiety disorders 1.

In terms of treatment, thyroid hormone replacement therapy is often effective in improving depressive symptoms associated with hypothyroidism, and some patients may need both thyroid treatment and conventional depression treatments like antidepressants for full symptom resolution. However, the treatment approach should be individualized and guided by a healthcare provider, taking into account the patient's specific needs and medical history.

From the Research

Hypothyroidism and Depression

• There is an established relationship between hypothyroidism and depression, with studies demonstrating that somatostatin and serotonin influence the hypothalamus-pituitary-thyroid axis, linking hypothyroidism to depression 2.
• Undiagnosed, untreated, or undertreated patients with hypothyroidism are at increased risk of developing depression, and autoimmune thyroiditis is also associated with an increased risk of depression 2.
• Elevated thyroid-stimulating hormone (TSH), antithyroglobulin (TgAb), and thyroid peroxidase antibodies (TPOAb) levels have all been linked to depression and an increased risk of suicide 2.

Pathogenesis and Management

• Hypothyroidism has been linked to depression, with irrefutable evidence that it triggers affective disease and psychic disorders 3.
• Depressive patients have a higher frequency of hypothyroidism, and patients with hypothyroidism have a higher occurrence of depressive syndrome 3.
• Thyroid peroxidase antibodies have been positively associated with trait markers of depression, and depressive symptomatology is variable and influenced by susceptibility and the degree of thyroid failure 3.

Treatment and Therapy

• Treating underlying hypothyroidism with thyroid replacement therapy could significantly improve mood disorders such as depression 2.
• Levothyroxine therapy is used as adjunctive therapy to antidepressants in the management of depression and is known to improve symptoms of depression rapidly when compared to antidepressants alone 2.
• Increasing levothyroxine dose can improve depressive mood in older adults undergoing thyroid hormone replacement therapy, without significant hyperthyroid symptoms or signs 4.
• Thyroid hormones, particularly triiodothyronine (T3), have been used for several decades as accelerators and augmenters of antidepressant response 5.

Association and Meta-analysis

• Hypothyroidism is considered a cause of or a strong risk factor for depression, with a systematic review and meta-analysis estimating the association of hypothyroidism and clinical depression in the general population 6.
• The meta-analysis found a modest association between hypothyroidism and clinical depression, with an odds ratio of 1.30, and a stronger association with overt than with subclinical hypothyroidism 6.