What testing and blood work should be done for a patient with hypothyroidism on levothyroxine presenting with muscle twitches and incontinence after stopping Otezla for psoriasis?

Blood Work and Testing for a Patient with Hypothyroidism and Muscle Twitches After Stopping Otezla

A comprehensive thyroid panel, electrolyte studies, and neuromuscular workup should be performed for this patient with hypothyroidism experiencing muscle twitches and incontinence after stopping Otezla. The symptoms suggest possible thyroid dysfunction, electrolyte imbalances, or medication withdrawal effects requiring thorough investigation.

Initial Laboratory Testing

• Complete thyroid function tests: TSH and free T4 to assess adequacy of current levothyroxine dosage (25 mcg) and rule out undertreated hypothyroidism 1
• Comprehensive metabolic panel: To evaluate electrolytes, particularly calcium, sodium, and potassium levels that could contribute to muscle twitching 1
• Serum calcium: To rule out hypocalcemia which can cause tetany and muscle twitching 2
• Magnesium and phosphorus levels: Deficiencies can contribute to neuromuscular symptoms 1

Additional Endocrine Evaluation

• Morning cortisol and ACTH levels: To evaluate for possible adrenal insufficiency which can present with neuromuscular symptoms 1
• Parathyroid hormone (PTH): If calcium abnormalities are detected 1
• Anti-thyroid peroxidase (TPO) antibodies: To assess for autoimmune thyroid disease, which is common in patients with other autoimmune conditions like psoriasis 1, 3, 4

Neuromuscular Assessment

• Creatine kinase (CK): To evaluate for possible myositis or muscle damage 1
• Aldolase, AST, ALT, LDH: Additional markers of muscle inflammation 1
• Electromyography (EMG): To characterize the muscle twitches and determine if they represent fasciculations, myokymia, or other neuromuscular phenomena 1, 5
• Nerve conduction studies: To evaluate for possible peripheral neuropathy 1

Urological Workup

• Urinalysis: To evaluate for urinary tract infection or other causes of incontinence 1
• Post-void residual measurement: To assess bladder function 1

Medication-Related Testing

• Drug withdrawal assessment: Evaluate timing relationship between Otezla discontinuation and symptom onset 1
• Review of current medications: Assess for potential drug interactions with levothyroxine 1

Imaging Studies

• Consider MRI of affected muscle groups: If symptoms persist and laboratory findings suggest myositis 1, 5
• Consider brain MRI: If central nervous system involvement is suspected 1

Special Considerations

• The patient's hypothyroidism requires careful monitoring as inadequately treated hypothyroidism can cause muscle weakness, fatigue, and neurological symptoms 1
• The temporal relationship between stopping Otezla (apremilast) and symptom onset suggests a possible withdrawal effect or unmasking of an underlying condition 1
• Recent research has shown associations between psoriasis and thyroid dysfunction, suggesting the need for thorough thyroid evaluation 3, 4
• The incontinence associated with muscle twitches suggests possible involvement of pelvic floor muscles or neurological pathways requiring specialized assessment 1

Follow-up Testing

• Repeat thyroid function tests after any adjustment to levothyroxine dosage 1
• Consider referral to neurology if initial workup is inconclusive 1
• Consider referral to rheumatology if autoimmune etiology is suspected 1

Remember that muscle twitches with incontinence represent a significant impact on quality of life and require thorough investigation to identify the underlying cause and appropriate treatment.