Why is thyroid function assessment crucial in a pregnant or postpartum woman presenting with mania?

Why Thyroid Function Assessment Is Critical in Perinatal Mania

Thyroid dysfunction—both hypothyroidism and hyperthyroidism—can directly cause or mimic mania in pregnant and postpartum women, making thyroid function testing mandatory before attributing psychiatric symptoms to primary bipolar disorder or postpartum psychosis. 1, 2

Hypothyroidism Can Present as Acute Mania

The Paradoxical Presentation

• Severe hypothyroidism can manifest as acute mania with psychotic features, including pressured speech, decreased need for sleep, distractibility, religious delusions, and paranoid ideation—symptoms indistinguishable from primary bipolar mania. 1
• This presentation, termed "myxedema psychosis" or "myxedema madness," represents a psychiatric emergency that resolves rapidly with thyroid hormone replacement rather than requiring long-term mood stabilizers. 1
• A case series documented complete resolution of manic symptoms in a 26-year-old woman with surgically absent thyroid who presented with first-episode mania; her TSH was severely elevated with undetectable thyroxine, and combined levothyroxine plus liothyronine produced rapid symptom resolution. 1

Postpartum Thyroiditis as a Trigger

• Postpartum thyroiditis occurs in up to 11.5% of women at 6 months postpartum and can precipitate acute mania through the hypothyroid phase of the condition. 3, 2
• One documented case showed acute mania triggered specifically by hypothyroidism secondary to postpartum thyroiditis, emphasizing that the postpartum period creates dual risk from both psychiatric and endocrine instability. 2
• Postpartum thyroiditis is diagnosed by new onset of abnormal TSH or free T4 levels after delivery, and the risk of permanent hypothyroidism is highest in women with elevated TSH and positive antithyroid peroxidase antibodies. 4

Hyperthyroidism and Thyroid Storm Mimic Mania

Clinical Overlap with Manic Symptoms

• Thyroid storm presents with altered mental status (nervousness, restlessness, confusion), tachycardia, fever, and agitation—a constellation that overlaps substantially with acute mania and can be misdiagnosed as primary psychiatric illness. 4, 5
• Untreated hyperthyroidism during pregnancy increases risk of severe preeclampsia, preterm delivery, heart failure, miscarriage, and low birth weight, making rapid differentiation from psychiatric mania life-saving for both mother and fetus. 5, 6

Biochemical Hyperthyroidism in Pregnancy

• Hyperemesis gravidarum is associated with biochemical hyperthyroidism (undetectable TSH, elevated free thyroxine index) that rarely causes clinical symptoms, but when symptomatic can produce anxiety, tremor, and agitation mimicking hypomania. 4

Thyroid Autoimmunity and Psychiatric Risk

Antibody-Mediated Mechanisms

• Thyroid autoantibodies (microsomal antibody and thyroid peroxidase antibody) are present in 46.5% and 63.9% of women with postpartum thyroid dysfunction, respectively, compared to only 1.7% and 4.9% in unaffected women. 3
• Although one study found no direct relationship between thyroid antibody status and current depression at 6 months postpartum, women with postpartum thyroid dysfunction who were diagnosed as anxious had significantly higher numbers of anxiety symptoms than controls. 3
• Autoimmune thyroid disease is present in approximately 4% of young females, and up to 15% are thyroid antibody-positive, creating a substantial at-risk population for both thyroid and psychiatric complications in the perinatal period. 7

Diagnostic Pitfalls and Screening Imperatives

When Thyroid Testing Is Mandatory

• All patients presenting with first-episode mania must be screened for thyroid dysfunction before assuming primary psychiatric illness, as misdiagnosis leads to inappropriate long-term psychotropic treatment when simple hormone replacement would suffice. 1
• The American College of Obstetricians and Gynecologists recommends screening pregnant women with symptoms of thyroid disease, history of thyroid disease, thyroid nodules, or goiter, though universal screening is not yet recommended. 4, 6
• TSH and free T4 levels should be evaluated in women who develop a goiter during pregnancy or after delivery, and evaluation may be appropriate for women who develop postpartum symptoms of hyperthyroidism or hypothyroidism—though clinical judgment is required because some symptoms overlap with normal postpartum physiology. 4

The Challenge of Clinical Diagnosis

• Postpartum thyroid dysfunction is identifiable by physicians only through abnormal thyroid function tests, not by clinical signs and symptoms, because there is no difference in hypo- or hyperthyroid clinical indices between cases and controls in the complex endocrine and psychological setting of the postpartum period. 3
• This means that relying on classic thyroid symptoms (cold intolerance, weight changes, fatigue) will miss the majority of cases, and biochemical screening is the only reliable detection method. 3

Treatment Implications

Rapid Symptom Resolution with Correct Diagnosis

• When mania is caused by hypothyroidism, combined levothyroxine and liothyronine produces rapid resolution of psychiatric symptoms, and correction of hypothyroidism improves response to antipsychotics if they are needed as bridge therapy. 1
• The preferred treatment for hypothyroidism-induced mania includes an atypical antipsychotic for acute symptom control plus thyroid replacement therapy, but the antipsychotic can often be discontinued once euthyroidism is achieved. 1

Avoiding Misattribution and Overtreatment

• Misdiagnosing thyroid-induced mania as primary bipolar disorder commits patients to unnecessary lifelong mood stabilizers, anticonvulsants, or antipsychotics with their attendant metabolic and teratogenic risks. 1
• Conversely, failing to treat underlying thyroid dysfunction in a truly bipolar patient will result in treatment-resistant mania and poor response to standard psychiatric medications. 1

Fetal and Neonatal Considerations

Maternal Thyroid Status Affects Offspring

• Untreated maternal hypothyroidism increases risk of preeclampsia, low birth weight, and neuropsychological defects in offspring, including possible decrements in cognitive development. 5
• Maternal hypothyroidism from iodine deficiency increases risk of congenital cretinism with growth failure, mental retardation, and neuropsychological defects. 5
• The newborn's physician must be informed about maternal thyroid disease (both hyperthyroidism and hypothyroidism) due to risk of neonatal thyroid dysfunction from transplacental antibody passage. 5, 6

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In summary: Thyroid function testing (TSH, free T4, and thyroid antibodies) is non-negotiable in any pregnant or postpartum woman presenting with mania because thyroid dysfunction is a reversible medical cause that requires fundamentally different treatment than primary psychiatric illness, and missing the diagnosis has catastrophic consequences for both maternal mental health and fetal neurodevelopment.