Hypothyroidism Secondary to Lithium Can Cause Constipation
Yes, hypothyroidism secondary to lithium therapy can cause constipation as one of its clinical manifestations. Constipation is a recognized symptom of hypothyroidism regardless of its etiology, including when it develops as a side effect of lithium treatment.
Hypothyroidism and Constipation Connection
- Hypothyroidism is characterized by several clinical manifestations including fatigue, muscle cramps, constipation, cold intolerance, hair loss, weight gain, and intellectual slowness 1
- Constipation is specifically listed as one of the key symptoms that should prompt suspicion of hypothyroidism in patients 1
- The American Gastroenterological Association recognizes hypothyroidism as one of the metabolic disturbances that can cause secondary constipation 1
Lithium-Induced Hypothyroidism
- Lithium therapy is a well-documented cause of thyroid dysfunction, with hypothyroidism being more common than hyperthyroidism 2, 3
- The prevalence of lithium-associated hypothyroidism ranges from 15% to 25.8% in different studies, with women having a higher risk than men 4, 5
- The risk of developing hypothyroidism increases with age, particularly in women over 50 years, reaching up to 50% by age 65 4
- Hypothyroidism can develop relatively quickly after starting lithium therapy, with a median time to abnormal thyroid tests of 341 days in one study 5 and 50% of patients requiring thyroid replacement therapy within 10 months of starting lithium in another study 2
Pathophysiology of Constipation in Hypothyroidism
- Thyroid hormones influence gastrointestinal motility through both direct effects on muscle cell receptors and indirect effects mediated by catecholamines 6
- Hypothyroidism can impair intestinal motility, leading to delayed transit time and resulting in constipation 6
- Constipation is frequently observed in hypothyroidism regardless of the cause, including when secondary to lithium therapy 6
- In severe cases, hypothyroidism may even cause chronic intestinal pseudo-obstruction syndrome 6
Clinical Implications and Management
- When evaluating constipation, hypothyroidism should be considered as a potential secondary cause 1
- The American Gastroenterological Association recommends thyroid function testing (TSH) as part of the evaluation of chronic constipation 1
- If constipation is present in a patient on lithium therapy, assessment for hypothyroidism should be performed 1
- Treatment of the underlying hypothyroidism with thyroid hormone replacement can help resolve constipation symptoms 1
- It's worth noting that lithium-associated hypothyroidism may be reversible in approximately 41% of patients after lithium discontinuation 2
Clinical Pearls and Pitfalls
- Constipation in patients on lithium therapy should prompt evaluation of thyroid function 1
- Motility-related digestive symptoms, including constipation, may sometimes be the first or only clue of thyroid dysfunction 6
- When treating both adrenal insufficiency and hypothyroidism, steroids should always be started prior to thyroid hormone to avoid an adrenal crisis 1
- Regular monitoring of thyroid function is recommended for patients on lithium therapy, especially women over 50 years of age 4