MON-385 - Progressive Severe Hypothyroidism Due to Medication Nonadherence with Minimal Clinical Manifestations in an Elderly Patient

Background:
Hypothyroidism is a common endocrine disorder, particularly in older adults, and is typically associated with symptoms such as fatigue, weight gain, constipation, and cold intolerance. However, the clinical presentation in elderly patients may be subtle or atypical, leading to delayed diagnosis. Severe biochemical hypothyroidism, characterized by markedly elevated TSH and low or undetectable thyroid hormone levels, is generally expected to produce significant clinical manifestations. We present a case of profound hypothyroidism discovered incidentally in an elderly patient with minimal symptoms despite progressive biochemical deterioration over several years.

Case Presentation:
An 86-year-old female presented following a mechanical fall. Initial evaluation revealed suspected pneumonia, dental infection, and orthostatic hypotension likely related to diuretic use in the setting of heart failure with reduced ejection fraction. Laboratory testing incidentally demonstrated a markedly elevated thyroid-stimulating hormone (TSH) level of 153 µIU/mL with undetectable free T4 and free T3.
Despite profound biochemical abnormalities, the patient denied typical hypothyroid symptoms, including fatigue, constipation or heat intolerance. Heart rate ranged from 55 to 91 beats per minute, sodium was within normal limits (135 mmol/L), and echocardiography showed no pericardial effusion.
Review of prior records revealed a progressive increase in TSH over several years (1.7 µIU/mL in 2021, 41.8 in 2023, 65.5 in 2024, and 80 in 2025), consistent with longstanding untreated hypothyroidism due to medication nonadherence.
The patient had been prescribed levothyroxine 100 mcg daily but reported not taking her medication. She was discharged on the same dose with outpatient endocrinology follow-up.

Conclusion:
This case highlights a striking discordance between biochemical severity and clinical presentation in hypothyroidism and emphasizes the importance of medication adherence and longitudinal monitoring, particularly in elderly patients, as gradual biochemical deterioration may remain clinically silent until advanced stages. Additionally, the presence of multiple comorbidities and acute conditions may obscure recognition of underlying endocrine disorders

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