New thyroxine treatment in older adults beginning lithium therapy: implications for clinical practice.
OBJECTIVE
The authors sought to determine the incidence of lithium-induced hypothyroidism in a population-based cohort of older adults beginning lithium therapy and thereby to inform clinical guidelines on the frequency of monitoring necessary in this group.


METHODS
The authors conducted a population-based observational cohort study using four administrative databases that contained information on over 1.3 million older adults in Ontario who receive universal healthcare coverage in terms of physician services, drugs, and hospitalizations. Over an 18-month period, they studied adults age>or=65 who were newly prescribed lithium or valproate, monitoring subjects for initiation of T4 therapy (as a proxy for hypothyroidism) while they continued their lithium use.


RESULTS
The authors identified 1,705 new users of lithium and 2,406 new users of valproate with similar baseline characteristics. Lithium users were significantly more likely to be treated with T4 than were valproate users. The rate of T4 treatment per 100 person-years was 5.65 in the lithium group and 2.70 in the valproate group.


CONCLUSIONS
T4 treatment was initiated in almost 6% of lithium-treated patients, suggesting the possibility that hypothyroidism developed twice as frequently among these patients as would be expected among a mixed-age population. Increased vigilance and continued monitoring of thyroid functioning for at least 2 years is necessary in older adults beginning lithium therapy.
Shulman
Kenneth I
KI
Dept. of Psychiatry and the Institute for Clinical Evaluative Sciences, Sunnybrook and Women's College Health Sciences Centre, 2075 Bayview Avenue, Toronto, Ontario, M4N 3M5, Canada. Ken.Shulman@sw.ca
Sykora
Kathy
K
Gill
Sudeep S
SS
Mamdani
Muhammad
M
Anderson
Geoffrey
G
Marras
Connie
C
Wodchis
Walter P
WP
Lee
Philip E
PE
Rochon
Paula
P
D000368:Aged; D000369:Aged, 80 and over; D000927:Anticonvulsants / Q000627:therapeutic use; D014150:Antipsychotic Agents / Q000009:adverse effects* / Q000627:therapeutic use; D001714:Bipolar Disorder / Q000188:drug therapy*; D015331:Cohort Studies; D016903:Drug Monitoring; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000139:chemically induced* / Q000188:drug therapy* / Q000453:epidemiology; D015994:Incidence; D016651:Lithium Carbonate / Q000009:adverse effects* / Q000627:therapeutic use; D008297:Male; D019370:Observation; D011159:Population Surveillance; D013974:Thyroxine / Q000008:administration & dosage / Q000627:therapeutic use*; D014635:Valproic Acid / Q000627:therapeutic use
D000927:Anticonvulsants; D014150:Antipsychotic Agents; D016651:Lithium Carbonate; D014635:Valproic Acid; D013974:Thyroxine