Late onset radioiodine-induced hypothyroidism presenting wit
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Alapan Bandyopadhyay
Late onset radioiodine-induced hypothyroidism presenting with psychosis 14 years after treatment.
Radioiodine treatment-induced hypothyroid psychosis is uncommon. Our literature search shows only three cases of hypothyroid psychosis developed within 3 months after the radioiodine treatment. Our case represents the first case of radioiodine-induced hypothyroidism presenting as psychosis much later (14 years) after the radioiodine treatment. A 60-year-old Chinese lady, with long-standing primary hypothyroidism due to the radioiodine treatment performed 14 years ago, presented with a 1-week history of hallucination, delusion and agitation. She was not on thyroid replacement. Thyroid function test done 14 years ago and again upon her admission to our facility was consistent with primary hypothyroidism. General blood tests and brain imaging were unremarkable. Her psychotic features resolved within 1 week with thyroid replacement and 9 days of antipsychotics. No further relapse of psychosis was noted. This emphasizes that radioiodine-induced hypothyroidism can go unnoticed for many years and present much later solely as psychosis.

Case Report

Madam X, a 60-year-old Chinese lady, was admitted with a history of 1 week of altered mental status after a fall. Her daughter noted her to be withdrawn, agitated, having an auditory hallucination of her children asking her to meet them at a café and a visual hallucination of a doctor pressing the call bell. She was a housewife who managed housework and grocery shopping well before the fall. She had no past history or a family history of psychiatric disorders. There was no history of substance abuse.

Her physical examination was unremarkable. Initial investigations showed a normocytic, normochromic anaemia, normal liver enzymes and renal function with no gross electrolyte abnormalities. Computed tomography of the brain, chest X-ray and urinalysis were unremarkable.

Subsequent investigations (Table 1) included a normal magnetic resonance imaging of her brain and thyroid function test that showed primary hypothyroidism.

Table 1:
Summary of laboratory and imaging result of our patient during admission
Investigation Result Reference

Free thyroxine (pmol/l) <2 8–21

TSH (mIU/l) 45.54 0.34–5.6

Free T3 (pmol/l) 2.3 3.5–6.0

Anti-thyroperoxidase ab Negative <50 IU/ml

Anti-thyroglobulin <0.9 IU/ml

CT brain No acute intracranial
haemorrhage or skull fracture

MRI brain No acute infarct or intracranial

0 min cortisol 161 nmol/l

30 min cortisol 573 nmol/l

60 min cortisol 704 nmol/l

ACTH 6.6 0–10.2 pmol/l

Further history from the patient's daughter revealed that Madam X had received radioiodine therapy for hyperthyroidism 14 years ago. She has since then not taken any thyroxine replacement or had any follow-up. The last available thyroid function test done 14 years ago showed primary hypothyroidism: free thyroxine 9.2 pmol/l (9.6–19.1) and thyroid stimulating hormone (TSH) 38.7 mU/l (0.36–3.25). She was not noted to have hypothyroid symptoms by her daughter.

Our psychiatrist concluded that Madam X was psychotic with delusions, thought disorder and hallucinations. Olanzapine and lorazepam were started for behaviour control. Levothyroxine was started at a dose of 25 µg daily and after 3 days, it was increased to a dose of 50 µg daily. Her psychotic features resolved within a week.

Upon discharge, she was advised to continue taking the olanzapine and thyroxine. She however did not take olanzapine at all. She was reviewed by the same psychiatrist twice (2 weeks and 2 months) after her discharge. No relapse of psychosis was reported by the patient and her daughter without antipsychotics. She was discharged from the psychiatrist follow-up.

Six weeks after discharge, the thyroid function test showed improvement and levothyroxine dose was increased to 75 µg daily and to 100 µg daily after another 3 months. The thyroid function test subsequently became normal (see Table 2 for thyroid function test trending).

Table 2:
Thyroid function test Free thyroxine (pmol/l) TSH (mIU/l)

12 July 2014 (on admission) <2 45.54

4 September 2014 7 22.58

20 November 2014 9 15.43

16 February 2015 19 2.03

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