What are the possible causes of excessive sweating in a patient with elevated Thyroid-Stimulating Hormone (TSH) and free Thyroxine (T4) levels, normal free Triiodothyronine (T3) levels, and a thyroid panel showing subnormal thyroid binding globulin, and what additional laboratory tests are warranted?

From the Guidelines

For a patient with excessive sweating, elevated TSH (>10), normal free T4 and T3, and thyroid antibody less than one, I recommend evaluating for subclinical hypothyroidism and other potential causes of hyperhidrosis, starting with a repeat thyroid panel to confirm results, as subclinical hypothyroidism typically presents with dry skin rather than sweating, as noted in the U.S. Preventive Services Task Force recommendation statement 1. Additional testing should include:

• Complete blood count
• Comprehensive metabolic panel
• Hemoglobin A1c
• Fasting glucose to rule out diabetes or infection Consider checking:
• Serum catecholamines
• 24-hour urinary metanephrines
• Plasma free metanephrines to evaluate for pheochromocytoma, as suggested by the screening for thyroid dysfunction guidelines 2 Assess cortisol levels with:
• 24-hour urinary free cortisol
• Overnight dexamethasone suppression test to rule out Cushing's syndrome Other helpful tests include:
• Serum calcium
• Parathyroid hormone for hyperparathyroidism
• Ferritin for anemia Medication review is essential as beta-blockers, antidepressants, and opioid withdrawal can cause sweating, as mentioned in the screening for thyroid dysfunction guidelines 3 If these tests are unrevealing, consider referral to neurology to evaluate for neurologic causes of hyperhidrosis or to dermatology for primary focal hyperhidrosis assessment. The discrepancy between the elevated TSH and normal thyroid hormones with excessive sweating suggests either subclinical hypothyroidism with an unrelated sweating disorder or another underlying condition causing both symptoms.

From the FDA Drug Label

They include the following: • General:fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating The patient's symptoms of excessive sweating could be related to hyperthyroidism or other conditions. Given the patient's elevated TSH and normal free T4 and T3 levels, it is essential to consider other possible causes of excessive sweating. Some potential causes and labs to check include:

• Anxiety or stress: consider screening for anxiety disorders
• Autonomic dysfunction: consider autonomic function tests
• Infections: consider complete blood count (CBC) and blood cultures
• Neurological disorders: consider electromyography (EMG) and nerve conduction studies
• Medication side effects: review the patient's medication list and consider alternative medications
• Other endocrine disorders: consider checking cortisol levels, growth hormone levels, and adrenal function tests It is crucial to conduct a thorough evaluation to determine the underlying cause of the patient's symptoms. 4

From the Research

Possible Causes of Elevated TSH and Normal Free T4 and T3

• Subclinical hypothyroidism, defined as an elevated serum thyroid-stimulating hormone (TSH) level along with a normal free thyroxine (T4) level 5, 6
• Autoimmune thyroiditis, which is the most common cause of subclinical hypothyroidism 6
• Transient elevation of TSH, which can occur in up to 50% of cases and may normalize spontaneously after 2-3 months 7
• Physiologically higher TSH levels in older adults, which can lead to overdiagnosis and overtreatment of subclinical hypothyroidism in this population 6, 7

Additional Labs and Testing

• Thyroid peroxidase antibodies to check for autoimmune thyroiditis 6
• Thyroid ultrasound to evaluate the thyroid gland and check for any nodules or abnormalities
• Complete blood count (CBC) and electrolyte panel to rule out other underlying conditions that may be contributing to the patient's symptoms
• Lipid profile to assess the risk of cardiovascular disease, which may be increased in patients with subclinical hypothyroidism 6

Considerations for Treatment

• Treatment may be indicated for patients with subclinical hypothyroidism and serum TSH levels of 10 mU/L or higher, or for young and middle-aged individuals with symptoms consistent with mild hypothyroidism 6
• Levothyroxine therapy may be associated with iatrogenic thyrotoxicosis, especially in elderly patients, and there is no evidence that it is beneficial in persons aged 65 years or older 6, 7
• Pregnant women with subclinical hypothyroidism may require special consideration and treatment to prevent adverse outcomes for both the mother and the fetus 7, 8