title: Effect of steroid replacement on thyroid function and thyroid autoimmunity in Addison's disease with primary hypothyroidism.
abstract: BACKGROUND
  Steroid replacement without thyroxine supplementation normalizes thyroid function test (TFT) in some but not all Addison's disease patients with primary hypothyroidism. Both autoimmune and nonautoimmune mechanisms contribute to this improvement in TFT. However, the documentation of the change in thyroid autoimmunity after cortisol replacement is very limited in the literature. The aim of this study was to determine the effect of steroid replacement on TFT and anti-thyroid peroxidase antibody (anti-TPO-Ab) titer in Addison's disease with primary hypothyroidism.
  
  
  METHODS
  This observational study was conducted in a tertiary care center in South India. Six Addison's disease patients with primary hypothyroidism, who were only on steroid replacement, were included in the study. Low serum cortisol (<83 nmol/L) with high plasma adrenocorticotropic hormone (>22 pmol/L) and/or hyperpigmentation of skin/mucous membranes was considered as the diagnostic criteria for Addison's disease. Primary hypothyroidism (both overt and subclinical) was defined as high thyroid stimulating hormone (TSH) with/without low free thyroxine (fT4). TFT and anti-TPO-Ab were performed before and after steroid replacement in all of them.
  
  
  RESULTS
  Poststeroid replacement, there was a normalization of TSH in all but one subjects. In overt hypothyroidism patients, fT4 also normalized. The improvement in TFT was not associated with decreasing titer of the anti-TPO-Ab in all six patients. However, there was a significant difference in TSH after steroid replacement compared to the baseline status.
  
  
  CONCLUSIONS
  The concept of normalization of primary hypothyroidism with cortisol replacement in patients with Addison's disease should be recognized to avoid iatrogenic thyrotoxicosis caused by thyroxine replacement. Both autoimmune and nonautoimmune mechanisms contribute to these alterations.
authors.affiliation: Department of Endocrinology and Metabolism, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India.
authors.forename: Jaya Prakash
authors.initials: JP
authors.lastname: Sahoo
authors.affiliation: Department of Endocrinology and Metabolism, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India.
authors.forename: Jayakumar
authors.initials: J
authors.lastname: Selviambigapathy
authors.affiliation: Department of Endocrinology and Metabolism, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India.
authors.forename: Sadishkumar
authors.initials: S
authors.lastname: Kamalanathan
authors.affiliation: Department of Radiodiagnosis, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India.
authors.forename: K
authors.initials: K
authors.lastname: Nagarajan
authors.affiliation: Department of Endocrinology and Metabolism, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India.
authors.forename: Muthupillai
authors.initials: M
authors.lastname: Vivekanandan
keywords: Addison's disease; anti-thyroid peroxidase antibody; autoimmunity; cortisol; hypothyroidism