Postpartum thyroid dysfunction: clinical assessment and relationship to psychiatric affective morbidity

OBJECTIVE Postpartum thyroid dysfunction (PPTD), diagnosed using biochemica l criteria, is usually transient with a wide range of reported prevalence r ates. The specific clinical and psychiatric morbidity associated with PPTD is still uncertain. The aims of the study were to determine the point preva lence of PPTD in Australian women at 6 months postpartum and to assess the specific clinical and psychiatric morbidity in these women. DESIGN Women who were Caucasian, aged 20-45 years and 4.5-5.5 months postpa rtum, were randomly selected and invited into the study. The respondents we re assessed for biochemical and psychiatric morbidity. PPTD for this study was defined as TSH or free T-4 outside the adult reference range. A double blind clinical assessment of PPTD women and their matched controls used sta ndardized clinical hypo- and hyperthyroid clinical indices, PATIENTS From the total randomly selected sample size of 1816 women, 748 pa rticipated. MEASUREMENTS Biochemical measurements were serum TSH, free T-4, microsomal antibody (MsAb) and thyroid peroxidase antibody (TPOAb), and thyroid recept or antibodies (only in women with low TSH). Psychiatric assessment involved screening all participants using the General Health Questionnaire 28, foll owed by classifying and quantifying severity of cases using DSM-III-R categ ories for depression and anxiety. Clinical signs and symptoms of hypo- and hyper-thyroidism were measured using weighted standardized indices. Thyroid size was assessed by palpation. Achilles tendon reflex time was measured b y photomotograph. RESULTS The prevalence of PPTD in the participants was 11.5% (95% Cl 9.2-13 .8%), giving a minimum prevalence for the randomly selected sample of 4.7% (95% Cl 3.7-5.7%). In the PPTD women, 54% had an elevated TSH, 30% had a su ppressed TSH and the remainder had a low fT(4) and normal TSH. Positive thy roid autoantibody titres in the PPTD group were 46.5% for microsomal antibo dy (MsAb) and 63.9% for thyroid peroxidase antibody (TPOAb), and in the non -PPTD group were 1.7% and 4.9%, respectively, The 6 month point prevalence rates of depression, generalized anxiety disorder and panic disorder and/or agoraphobia were 9.4%, 1.4% and 3.1%, respectively. No relationship was fo und between PPTD status and the diagnosis of current depression or between thyroid antibody status and current depression. In women who were diagnosed as anxious at the time of assessment, the number of anxiety symptoms was h igher in the PPTD group (P < 0.05). There was no difference in signs and sy mptom scores for the hypo- and hyperthyroid clinical indices between PPTD w omen and their controls. CONCLUSION This study has shown a high prevalence of postpartum thyroid dys function but there was no difference in the clinical and psychiatric signs and symptoms between cases and controls. In the social, psychological, phys ical and endocrine setting of the postpartum period, women with postpartum thyroid dysfunction are identifiable by the attending physician only by the ir abnormal thyroid function tests.