Thyroid function in children with Prader-Willi syndrome (PWS) treated with growth hormone (GH)

Abstract

Objective: Children with PWS, may be at risk of central hypothyroidism after commencing GH treatment. FT4 (Free Thyroxine) and TSH (Thyroid Stimulating Hormone), recorded in Australian GH database, OZGROW, were used to assess thyroid function in PWS patients before and after GH treatment. Methods: Between 2003 and 2014, 30 PWS patients were identified who had at least one recorded FT4 test and 31 with at least one TSH test. FT4 and TSH results were standardized by expressing them as a % of the reference range (RR) - where RR was available. x % = 100x - LU - L, where x is the test result and U and L are the upper and lower values of the RR. Mean test results were calculated in the year before GH treatment and from 4 weeks post-GH in the 1st year of treatment. These were compared to an expected mean of 50%. For individuals who had two such before and after tests for both FT4 and TSH, their change in test % was recorded and these differences tested against 0 (paired t-test). Results: In the year prior to GH, for 19 patients who were tested for both FT4 and TSH, mean(SD) FT4 = 18.8(16.9)%, p = 2 × 10-7 with 3 below RR and TSH = 37.7(27.1)%, p = 0.06, all within RR. Similarly for 13 patients in the 1st year of treatment all were within RR and FT4 = 19.9(10.5)%, p = 3 × 10-7 and TSH=20.8(14.0)%, p = 7 × 10-6. 8 patients had both FT4 and TSH tests before and after (1st year) GH commencement thus enabling us to test mean change in test% (D%). For FT4 D% mean(SD) = +1.4(11.6), p = 0.7 and for TSH D% mean(SD) = -12.3(8.2), p = 0.004. Conclusions: Most PWS patients are in the low normal RR for both TSH and FT4 prior to GH although mean FT4 is lower with some patients falling below the RR. Following GH, TSH decreases further while FT4 remains at a similar low level. GH, through increased somatostatin release, decreases TSH but also increases deiodination of T4 to T3. Although no patients were reported as receiving thyroxine, this possibility needs exclusion.L720732092015-11-20 <br />