Clinical features and genetic analysis of four Brazilian kindreds with resistance to thyroid hormone.

OBJECTIVE: Resistance to thyroid hormone (RTH) is a dominantly inherited syndrome of reduced tissue responsiveness to thyroid hormone usually due to mutations located in the ligand-binding domain and adjacent hinge region of the thyroid hormone receptor beta (TRbeta). In the present report we describe the clinical and laboratory characteristics and the genetic analysis of patients with this rare disorder from a Brazilian population. PATIENTS: Four unrelated Brazilian families with diagnosis of RTH were studied. Age at diagnosis varied from 14 months to 29 years. RESULTS: All affected individuals were clinically euthyroid, except for one patient who presented immediately after birth with hyperthyroidism. All individuals had tachycardia and goitre, elevated concentrations of free thyroid hormones and reduced sensitivity to thyroid hormone. Direct sequencing analysis of the TRbeta gene revealed four previously reported mutations: c.949G-->A, c.1313G-->A, c.1357C-->A and c.1358dupC in families A, B, C and D, respectively. CONCLUSION: The present report shows that the frequent mutations described in the thyroid hormone receptor worldwide are also present in the Brazilian population, which is characterized by a variable ethnic background.

Thyroid hormones correlate with symptoms of hyperactivity but not inattention in attention deficit hyperactivity disorder.

The diagnostic validity of dividing attention deficit hyperactivity disorder (ADHD) into two distinct subgroups, one with and one without hyperactivity, is controversial since there have been no physiological differences demonstrated between these two subgroups. In this study, the relationship between thyroid hormones and symptoms of hyperactivity was examined in subjects with resistance to thyroid hormone (RTH) and their unaffected family members. Clinical data were collected on 152 subjects; 75 subjects with RTH and 77 family members without RTH. Each subject was assessed using DSM-III-R criterion based, structured psychiatric interviews, and Total T3 (TT3), Total T4 (TT4) and TSH concentrations were measured. The total number of ADHD symptoms were assigned to either inattention or hyperactivity subgroups using DSM-III-R criteria. The total number of ADHD symptoms were then reassigned to inattention or hyperactivity/impulsivity subgroups using DSM-IV criteria. Pearson R correlation coefficients were calculated separately for the RTH and unaffected family members groups in order to determine the relationships between TSH, TT3 and TT4 concentrations, and the DSM-III-R and DSM-IV symptom categories of ADHD in both groups. TSH concentrations were not significantly correlated with any of the symptom categories in either group. However, in the RTH group, both TT3 and TT4 concentrations were significantly and positively correlated with total symptoms of ADHD (DSM-III-R) as well as symptoms of inattention (DSM-III-R) and symptoms of hyperactivity (DSM-III-R). When DSM-IV criteria were used, which reassigns symptoms of impulsivity from the inattention to the hyperactivity category, only the positive correlation between TT3 and TT4 concentrations and symptoms of hyperactivity/impulsivity (DSM-IV) remained significant. In the group of unaffected family members, the relationship between TT3 concentrations and symptoms of hyperactivity/impulsivity (DSM-IV) was the only significant correlation. The data support the hypothesis that thyroid hormones may provide a physiological basis for the dichotomy between symptoms of inattention and symptoms of hyperactivity, particularly when DSM-IV criteria are applied.

Neurocognitive characteristics of individuals with resistance to thyroid hormone: comparisons with individuals with attention-deficit hyperactivity disorder.

Previous studies have demonstrated an association between resistance to thyroid hormone (RTH) and attention-deficit hyperactivity disorder (ADHD). To determine if the neurocognitive characteristics in individuals with RTH are similar to those observed in ADHD, 12 children with RTH from 7 families were matched to 12 children with ADHD without RTH. Subjects were administered standardized intellectual, developmental, and school achievement tests. Parent and teacher ratings of children's hyperactivity and attention were similar for both groups, as were measures of attention, impulsivity, and verbal IQ. Children with RTH displayed lower nonverbal intelligence (performance IQ = 85) and academic achievement (> 1-2 SD below the mean) when compared with those with ADHD only (performance IQ = 99; achievement within 2 SD). Although children with RTH have behavioral characteristics similar to those with ADHD, their significantly weaker abilities of perceptual-organization and lower school achievement suggest a more severe neurobehavioral impairment than ADHD.

ADHD and thyroid abnormalities: a research note.

Contradictory findings have been reported on associations between ADHD and thyroid abnormalities including the syndrome of generalized resistance to thyroid hormone. We systematically reviewed thyroid function in a large group of children and adolescents with ADHD (N = 132). We failed to find evidence of generalized resistance to thyroid hormone. Although mild laboratory abnormalities in thyroid function were observed in a minority of ADHD subjects, they were not different than rates reported in the literature for normal children.