Prevalence of growth hormone deficiency in Hashimoto's thyroiditis.

Abstract

Autoimmune hypophysitis can result in GH deficiency (GHD) and is associated with other autoimmune endocrine diseases like Hashimoto's thyroiditis. Recent studies suggest a high prevalence (5%) of GHD in Hashimoto's thyroiditis. Our objective was to establish the prevalence of GHD in patients with treated autoimmune hypothyroidism (AIH). We included patients with spontaneous AIH [thyroid peroxidase antibodies (TPO-Ab) >or=100 kU/liter], who were adequately treated with T(4) (TSH 0.2-5.0 mU/liter). Exclusion criteria were previous I(131) treatment, thyroid surgery, or a history of hypothalamic or pituitary disease. Patients were recruited via our outpatient clinics and via patient self-help organizations. We measured serum TSH, free T(4), TPO-Ab, and IGF-I. If the IGF-I concentration was below the 10th percentile of age-specific reference values, a GHRH/GH-releasing peptide (GHRP)-6 test was done. GHD was defined as a GH peak after GHRH/GHRP-6 below the 2.5th percentile of age-specific reference values. IGF-I concentration and GH peak after GHRH/GHRP-6 test were measured. From 860 patients who applied, 322 did not satisfy inclusion criteria (157 because TPO-Ab was <100 kU/liter, 165 because TSH was <0.2 or >5.0 mU/liter), and 23 had an exclusion criterion. In the remaining study population of 515 patients (476 female, 39 male), 49 patients (9.5%) had an IGF-I concentration below the 10th percentile. These patients underwent a GHRH/GHRP-6 test. Two patients had a GH peak below the 2.5th percentile. The prevalence of GHD in Dutch patients with AIH is 0.4% (two of 515).