Depression etiology: Hypothalamic-Pituitary-Thyroid Axis Dysregulation

We are almost done building up the discussion about potential causes or contributing factors for depression. This post will focus on the role of the thyroid. 

Evidence Supporting Thyroid Dysfunction In Depression

It’s well established that thyroid dysfunction is associated with depression. Some evidence to support the theory that thyroid function is linked to depression includes a significant number of depressed patients who are hospitalized have a diagnosis of hypothyroidism (around 10%), thyroiditis is more common in mood disorders, patients with rapid cycling bipolar disorder are more likely to have hypothyroidism, and triiodothyronine (T3) is used as a augmentation strategy for difficult to treat depression.

One of the things we need to do prior to making a diagnosis of depression is to rule out potential medical causes. Looking for the following signs and symptoms, as well as laboratory testing can be helpful in assessing thyroid function.

The following symptoms are common in Hypothyroidism

  • Fatigue 
  • Cold intolerance 
  • Impaired memory and concentration 
  • Constipation 
  • Weight gain 
  • Shortness of breath 
  • Hoarse voice 

The following Signs may be present

  • Dry skin 
  • Cool extremities 
  • Hair loss 
  • Low pulse rate 
  • Delayed deep tendon reflexes 
  • Carpal tunnel syndrome 

Lab Testing and Physical Exam

Lab testing for TSH levels is the best initial test. It may need to be repeated in a few weeks to ensure the levels are truly elevated. Another way to help make the diagnosis is order a free T4 blood level to determine if this is subclinical hypothyroidism. If a lump or a mass is felt on thyroid during physical exam diagnostic imaging may be required. The presence of antibodies against thyroid peroxidase (Anti-TPO) provides evidence to support autoimmune thyroiditis as the cause of hypothyroidism.

Treatment For Hypothyroidism

Treatment includes hormone replacement. The long-acting form of thyroxine is called levothyroxine. A psychiatrist will likely recommend the primary care provider manage the diagnosis and treatment. 

Final Comments:

The need to treat depression while the work-up for hypothyroidism is occurring will depend on the clinical picture. Generally, I would prefer to wait until the hypothyroidism is treated adequately, but this is not always possible. 

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