What is the cause of thyrotoxicosis symptoms, such as sweating and restlessness, in a patient after surgery, considering potential diagnoses like iatrogenic (induced by medical treatment) thyrotoxicosis, de Quervain thyroiditis, Graves' disease, or simple goiter?

Post-Surgical Thyrotoxicosis: Most Likely Diagnosis

The most likely diagnosis in a patient developing sweating, restlessness, and thyrotoxicosis features after surgery is iatrogenic thyrotoxicosis from surgical manipulation causing transient destructive thyroiditis (similar to de Quervain's/subacute thyroiditis), which is self-limiting and resolves spontaneously within weeks.

Diagnostic Reasoning

Why Iatrogenic Thyrotoxicosis/Surgical Thyroiditis is Most Likely

• Surgical manipulation of the thyroid gland causes follicular disruption with release of preformed thyroid hormones into circulation, creating a transient thyrotoxic state that does not represent true hyperthyroidism 1
• This presents as painless thyroiditis with thyrotoxicosis (high free T4 or T3 with low/normal TSH) occurring within the first month post-surgery, with patients developing hypermetabolic symptoms including sweating, restlessness, palpitations, and anxiety 2, 3
• The temporal relationship to surgery is the key diagnostic clue - thyrotoxicosis developing in the immediate post-operative period strongly suggests surgical trauma as the etiology 3

Why Other Diagnoses Are Less Likely

Graves' Disease:

• Graves' disease would typically present with pre-existing symptoms before surgery, not acutely post-operatively 4
• Requires positive TSH receptor antibodies (TRAb) or thyroid stimulating immunoglobulin (TSI) for diagnosis 2, 3
• Would show increased radioiodine uptake on scanning, not the low/absent uptake seen in destructive thyroiditis 3

De Quervain's Thyroiditis (Classic):

• While the pathophysiology is similar to surgical thyroiditis, classic de Quervain's is typically painful and follows viral illness, not surgery 3
• The post-surgical variant is essentially the same mechanism but triggered by surgical trauma rather than viral infection

Simple Goiter:

• Simple goiter does not cause thyrotoxicosis - it represents thyroid enlargement without hormonal excess 4
• This diagnosis is incompatible with the clinical presentation of thyrotoxicosis

Diagnostic Workup

Initial Laboratory Assessment

• Measure TSH, free T4, and total T3 to confirm thyrotoxicosis (suppressed TSH with elevated free T4 and/or T3) 3
• Check thyroid peroxidase (TPO) antibody to support autoimmune thyroiditis 2, 3
• Obtain TRAb or TSI to exclude Graves' disease 2, 3

Imaging Studies to Confirm Transient Nature

• Radioiodine uptake scan (I-123 preferred) will show low or absent uptake in destructive thyroiditis, distinguishing it from Graves' disease which shows increased uptake 3
• Doppler ultrasound can measure thyroid blood flow - decreased flow indicates destructive process rather than overactive gland 3
• Technetium-99m pertechnetate scan is an alternative if recent iodinated contrast was used 2

Temporal Monitoring

• Repeat thyroid function tests every 2-3 weeks to document the natural progression 2, 3
• The thyrotoxic phase typically resolves within 2-14 weeks, often transitioning to hypothyroidism 3
• Most patients develop permanent hypothyroidism requiring lifelong replacement approximately 1-2 months after the thyrotoxic phase 2

Management Approach

Symptomatic Treatment Only

• Beta-blockers (atenolol or propranolol) for symptomatic relief of sweating, restlessness, palpitations, and anxiety 2
• Non-selective beta-blockers with alpha receptor-blocking capacity are preferred for more symptomatic patients 2
• Hydration and supportive care 2

Critical Pitfall to Avoid

• DO NOT initiate antithyroid drugs (methimazole, propylthiouracil) or radioactive iodine treatment - these are ineffective and inappropriate for destructive thyroiditis since the thyroid is not overproducing hormone, just releasing preformed stores 3, 1
• Thionamides are only indicated for true hyperthyroidism (Graves' disease, toxic nodules) where the gland is actively synthesizing excess hormone 1, 5

Monitoring for Hypothyroidism

• Close surveillance is essential as most patients transition to hypothyroidism 2, 3
• Initiate levothyroxine replacement when TSH becomes elevated and free T4 drops 2
• If both adrenal insufficiency and hypothyroidism are present, always start steroids before thyroid hormone to avoid precipitating adrenal crisis 2

When to Escalate Care

• Grade 3-4 symptoms (severe, life-threatening, unable to perform activities of daily living) require hospitalization and endocrine consultation 2
• Consider endocrine referral for persistent thyrotoxicosis lasting more than 6 weeks 2
• Severe cases may require additional therapies including steroids, saturated solution of potassium iodide (SSKI), or rarely surgery 2