title: Target Gland Dysfunction Following External Cranial Radiation for Extrasellar Tumours.
abstract: BACKGROUND
  Diseases of the pituitary gland manifest as increased or decreased production of one or more of these hormones that in turn trigger a series of secondary hormonal changes in target glands (Thyroid, Adrenal and Gonad). Dysfunction of target glands may follow treatment with external radiation when hypothalamo-pituitary axis lies within the field of radiation. The present study has been undertaken with the aim to study target gland dysfunction and their relationship with dose of radiotherapy and duration after radiotherapy in patients who have received extracranial radiation for extrasellar tumours.
  
  
  METHODS
  In this study, 96 patients who underwent cranial radiation 12 months ago were evaluated. Basal 8 am venous blood samples were taken for estimation of triiodothyronine (T3), thyroxin (T4), thyrotropin stimulating hormone (TSH) and basal cortisol estimation. Pooled samples (three samples taken 20 minutes apart and pooled together) were taken for LH, FSH and testosterone (TE) estimation. Insulin tolerance test was performed for stimulated cortisol levels.
  
  
  RESULTS
  Target gland dysfunction was present in 72 (75%) patients. Hypogonadism was present in 48 (53%) of post-pubertal patients. 36% of male patients had hypogonadism whereas 100% of female patients had hypogonadism. Patients with hypogonadism were older, received higher doses of radiation and evaluated earlier after radiotherapy than without hypogonadism. Serum testosterone level declined significantly with increasing doses of radiation. Hypoadrenalism was present in 44 patients (46%). There was no significant difference of age, radiation dose and radiation fraction among patients with or without adrenal insufficiency. Proportion of patients with hypoadrenalism increased with increasing duration after radiotherapy. Hypothyroidism was present in 12 patients (13%). Proportion of patients with hypothyroidism doubled with increasing dose of radiation. Serum T3 level declined significantly with increasing doses of radiation. Patients with hypothyroidism had significantly low T3 and T4 level, but significantly higher TSH and basal and peak cortisol levels than patients without hypothyroidism.
  
  
  CONCLUSIONS
  Target gland dysfunction is common after extracranial radiation for extrasellar tumours. Hypogonadism was the commonest followed by hypoadrenalism and hypothyroidism. Target gland dysfunction was related to age, radiation dose and duration after radiotherapy, but not with fraction of radiation.
authors.affiliation: Classified Specialist (Medicine & Endocrinology), Command Hospital (Central Command), Lucknow-226 002.
authors.forename: M K
authors.initials: MK
authors.lastname: Garg
keywords: Adrenal insufficiency; Cranial radiation; Hypogonadism; Hypothyroidism