Management of Newly Diagnosed Hypothyroidism in a 59-Year-Old Patient

Telephone Consultation Approach

This patient has overt hypothyroidism (TSH 7.7 mU/L with low T4 9.6 mmol/L) and requires immediate initiation of levothyroxine therapy. 1

Confirm the diagnosis and assess urgency:

Verify these are fasting morning labs taken at least 4 hours away from any interfering medications (calcium, iron, proton pump inhibitors) 2
Ask specifically about symptoms: fatigue, weight gain, cold intolerance, constipation, hair loss, depression, or cognitive changes 1, 3
Screen for cardiac symptoms (chest pain, palpitations, shortness of breath) or history of coronary artery disease, as this affects starting dose 1, 2
Inquire about pregnancy plans, as this requires more aggressive TSH normalization 1

Critical safety screening before prescribing:

Rule out adrenal insufficiency symptoms (orthostatic dizziness, salt craving, hyperpigmentation), as starting levothyroxine before treating adrenal insufficiency can precipitate adrenal crisis 3, 2
Document current medications, particularly anticoagulants (warfarin), diabetes medications, digitalis, or antidepressants, as levothyroxine interacts significantly with these 2

Starting dose for this 59-year-old patient:

Full replacement dose of approximately 1.6 mcg/kg/day is appropriate since she is under 70 years old 1
If she has cardiac disease or multiple comorbidities, start conservatively at 25-50 mcg/day instead 1, 2
For a typical 70 kg woman without cardiac disease, this translates to approximately 100-112 mcg daily 1

Prescribing instructions:

Take levothyroxine 30-60 minutes before breakfast on an empty stomach for optimal absorption 4
Separate from calcium, iron, proton pump inhibitors, or antacids by at least 4 hours 2
Emphasize this is lifelong therapy that should not be stopped 5

Initial follow-up schedule:

Recheck TSH and free T4 in 6-8 weeks after starting therapy 1, 2
Target TSH range of 0.5-2.0 mIU/L for optimal replacement 5, 6
If cardiac disease present, consider repeating within 2 weeks rather than waiting full 6-8 weeks 1

Dose adjustment protocol:

Adjust by 12.5-25 mcg increments based on TSH results 1
Continue 6-8 week monitoring intervals until TSH stabilizes in target range 1, 2
Once stable, monitor TSH every 6-12 months or with symptom changes 1

Check for autoimmune etiology:

Order anti-TPO antibodies if not already done, as positive antibodies indicate Hashimoto's thyroiditis and predict higher progression risk (4.3% vs 2.6% annually) 1, 3
This doesn't change immediate management but informs prognosis 1

Medication interactions to address:

If on warfarin: levothyroxine increases anticoagulant response, requiring closer INR monitoring and potential dose reduction 2
If diabetic: thyroid hormone replacement may worsen glycemic control, requiring increased antidiabetic medication 2
If on digitalis: may need increased digitalis dose as hypothyroidism is corrected 2

Undertreatment risks:

Persistent hypothyroid symptoms, adverse cardiovascular effects, and impaired quality of life 1
Inadequate treatment particularly problematic if pregnancy occurs 1

Overtreatment risks:

Iatrogenic hyperthyroidism occurs in 14-21% of treated patients 1
Increases risk for atrial fibrillation (especially in elderly), osteoporosis, fractures, and cardiac complications 1, 5
Approximately 25% of patients are unintentionally maintained on excessive doses 1

Compliance issues:

If TSH remains elevated despite adequate dosing, suspect poor adherence, malabsorption, or drug interactions before increasing dose 5, 6
Taking levothyroxine with food or coffee significantly reduces absorption 4

Lithium-induced hypothyroidism considerations:

Hypothyroidism can persist after lithium discontinuation, as appears to be the case here (stopped 2 years ago) 1
This represents permanent thyroid damage requiring lifelong replacement 1
No special dosing adjustments needed compared to other causes of hypothyroidism 1