Efficacy of Levothyroxine in Migraine Headaches in Children with Subclinical Hypothyroidism

Table of Contents

Materials & Methods

In a quasi- experimental study, the severity and monthly frequency of headache of 5 to 15-year-old migraineur children with subclinical hypothyroidism who were referred to the pediatric neurology clinic of Shahid Sadoughi University of Medical Sciences,Yazd, Iran between January 2010 and February 2011 and were treated with levothyroxine for two months were evaluated. The sample size of 25 children was assessed based on Z formula and a confidence interval of 95% with 80% power to detect any significant difference between the two groups with a significance level of 0.05.

The diagnostic criteria for migraine headache in this study were based on the second edition of International Headache Society Classification by taking history and clinical examination (8).

Children with hemiplegic migraine, basilar-type migraine, retinal migraine, childhood periodic syndromes as migraine variants (cyclic vomiting, abdominal migraine and benign paroxysmal vertigo of childhood), children with epilepsy, systemic diseases such as asthma, diabetes mellitus, hepatic and renal diseases, definite secondary headaches, previously diagnosed hypothyroidism or hyperthyroidism and those who had taken drugs that had affected thyroid functions during the past two months were excluded.

Scoring of the severity of the headache, which was between 0 and 10 points, was done by the patients. Zero represented no pain and 10 points was the most severe pain. Classification of the severity of headache was done as follows: mild, 1-3; moderate, 4-7; and severe, 8-10. After diagnosis of migraine headache in patients based on clinical evaluation, free thyroxin (T4) and thyroid stimulating hormone (TSH) serum levels were measured for evaluating thyroid functions in all of the children. According to Nelson Textbook of Pediatrics, normal values of serum free T4 level at ages 3-10 and in more than 10-year-old children are 5.5 -12.8 and 4.2 -13 microgram per deciliter (μg/dL), respectively. The TSH level is also 0.7-6.4 miliunit per liter (mIU/L) in 5 to 15-year-old children. When the child has no clinical sign of overt hypothyroidism, but the TSH level is more than 4.5 mU/L and either of T4 or free T4 level is normal, it is defined as subclinical hypothyroidism (9).

Serum TSH levels were measured by the third generation of radioimmunoassay methods (chemiluminescent assays) in the reference laboratory of Shahid Sadoughi University of Medical Sciences,Yazd, Iran.

If a patient had a low T4 level, it would be considered as overt hypothyroidism and the child was excluded from the study. Then in the second phase of the study, migraineur children with subclinical hypothyroidism were treated with levothyroxine and were visited for two consecutive months and clinical information regarding the severity and monthly frequency of the headache were recorded through interviewing the patients and finally the patients’ condition were compared before and after treatment. The optimal level for TSH after treatment was considered as 0.4–4 mU/L (9).

The data were analyzed using Statistical Package for the Social Sciences version 15 (SPSS, Chicago, IL, USA). Chi-square test or Fisher exact test was used for data analysis of qualitative variables and the mean values were compared using independent T-test. Differences were considered significant at P values of less than 0.05.

An informed consent was obtained from the parents of migraineur children and this study has been approved by the Ethics Committee of Ali-ebn-Abitaleb School of Medicine, Islamic Azad University, Yazd Branch, Yazd, Iran.