title: Predictive value of pyramidal lobe, percentage thyroid uptake and age for ablation outcome after 15 mCi fixed dose of radioiodine-131 in Graves' disease.
abstract: OBJECTIVE
  The purpose was to find out the efficacy of fixed 15 mCi radioactive iodine-131 (RAI) dose and predictive values of various factors for inducing hypothyroidism in Graves' disease (GD).
  
  
  METHODS
  Retrospective study conducted from January 2012 till August 2014. Patients with GD who had a technetium-99m thyroid scan, thyroid antibodies, received fixed 15 mCi RAI and did follow endocrine clinics for at least 6 months were selected. RAI was considered successful if within 6 months of RAI therapy patients developed hypothyroidism.
  
  
  RESULTS
  Of the 370 patients with GD who had RAI during study period, 210 (57%) qualified study criteria. Mean age of patients was 48 ± 15 years with female: male ratio of 69:31, positive thyroid antibodies in 61%, means thyroid uptake of 15.09 ± 11.23%, and presence of pyramidal lobe in 40% of total population. Hypothyroidism was achieved in 161 (77%) patients while 49 (23%) patients failed to achieve it (remained either hyperthyroid or euthyroid on antithyroid medication). Patients who became hypothyroid were significantly younger with higher proportion of presence of thyroid antibodies and pyramidal lobe and lower percentage thyroid uptake than those who failed. Multiple logistic regression analysis revealed that age (odds ratio; OR = 2.074), pyramidal lobe (OR = 3.317), thyroid antibodies (OR = 8.198), and percentage thyroid uptake (OR = 3.043) were found to be significant prognostic risk factors for post-RAI hypothyroidism. Gender was found to have nonsignificant association with the development of hypothyroidism. Receiver operating characteristic analysis revealed age <42 years and thyroid uptake <15% as threshold values for the development of post-RAI hypothyroidism.
  
  
  CONCLUSIONS
  We conclude that fixed (15 mCi) RAI dose is highly effective in rendering hypothyroidism in patients with GD. Age (≤42 years), thyroid uptake (≤15%) and presence of pyramidal lobe are strong predictors of hypothyroidism and must be considered for selecting optimal RAI dose.
authors.affiliation: Department of Radiology, Section of Nuclear Medicine, Aga Khan University Hospital, Karachi, Pakistan.
authors.forename: Maseeh Uz
authors.initials: MU
authors.lastname: Zaman
authors.affiliation: Department of Nuclear Medicine, Dr. Ziauddin Hospital, Karachi, Pakistan.
authors.forename: Nosheen
authors.initials: N
authors.lastname: Fatima
authors.affiliation: Dow Medical College, Dow University of Health Sciences, Karachi, Pakistan.
authors.forename: Unaiza
authors.initials: U
authors.lastname: Zaman
authors.affiliation: Department of Radiology, Section of Nuclear Medicine, Aga Khan University Hospital, Karachi, Pakistan.
authors.forename: Zafar
authors.initials: Z
authors.lastname: Sajjad
authors.affiliation: Dow Medical College, Dow University of Health Sciences, Karachi, Pakistan.
authors.forename: Areeba
authors.initials: A
authors.lastname: Zaman
authors.affiliation: Dow Medical College, Dow University of Health Sciences, Karachi, Pakistan.
authors.forename: Rabia
authors.initials: R
authors.lastname: Tahseen
keywords: Fixed dose; Graves’ disease; pyramidal lobe; radioiodine-131; thyroid uptake