Long-term effects of growth hormone replacement therapy on thyroid function in adults with growth hormone deficiency

Marco Losa, Marina Scavini, Elisa Gatti, Alessandro Rossini, Sara Madaschi, Ilaria Formenti, Andrea Caumo, Christine A. Stidley, Roberto Lanzi

Research output: Contribution to journalArticle

Abstract

Background: Clinical studies on the effect of growth hormone (GH) on thyroid function in patients with GH deficiency are contradictory. Further, the majority of published observations are limited to the first 6-12 months of GH replacement therapy. The aim of our study was to estimate the incidence of clinically relevant hypothyroidism in a cohort of patients with adult GH deficiency (AGHD) during long-term therapy with recombinant human GH (rhGH). Methods: The study was designed as a retrospective collection of data on thyroid function in 49 AGHD patients of whom 44 (90%) had multiple hormone deficiency. Thirty-seven patients (76%) were on stable levothyroxine (LT4) replacement therapy (HYPO), and 12 (24%) were euthyroid (EUT). Therapy with rhGH was started at a dose of 3.5 μg/kg body weight and adjusted according to insulin-like growth factor-I (IGF-I) levels. At baseline, 6 months, 12 months, and yearly thereafter we measured free triiodothyronine (fT3), free thyroxine (fT4), thyroid-stimulating hormone, and IGF-I. Study outcome was fT4 level below the normal range (9 pmol/L), irrespectively of fT3 or thyroid-stimulating hormone levels. Results: During a follow-up of 115 patient-years, mean fT4 level decreased significantly, although remaining within the normal range (p = 0.0242; month 48 vs. baseline). The largest decrease was between baseline and month 6, when fT4 decreased of 1.43 pmol/L (95% confidence interval, 0.33-2.53) per 1 unit (μg/kg body weight) increase in rhGH dose. The incidence of hypothyroidism was 1.2 (HYPO group) and 6.7 (EUT group) events per 100 patient-years. Conclusion: We confirm that in patients with AGHD, rhGH therapy is associated with a small, although significant, decrement of fT4 in the first 6 months of replacement therapy. However, the incidence of hypothyroidism is low. Monitoring of thyroid function during rhGH therapy is advisable, particularly in the first year of therapy when the largest decrease in fT4 occurs.

Original languageEnglish
Pages (from-to)1249-1254
Number of pages6
JournalThyroid
Volume18
Issue number12
DOIs
Publication statusPublished - Dec 1 2008

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Hormone Replacement Therapy
Growth Hormone
Thyroid Gland
Hypothyroidism
Thyrotropin
Insulin-Like Growth Factor I
Thyroxine
Therapeutics
Incidence
Reference Values
Body Weight
Human Growth Hormone
Triiodothyronine
Outcome Assessment (Health Care)
Hormones
Confidence Intervals

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

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Long-term effects of growth hormone replacement therapy on thyroid function in adults with growth hormone deficiency. / Losa, Marco; Scavini, Marina; Gatti, Elisa; Rossini, Alessandro; Madaschi, Sara; Formenti, Ilaria; Caumo, Andrea; Stidley, Christine A.; Lanzi, Roberto.

In: Thyroid, Vol. 18, No. 12, 01.12.2008, p. 1249-1254.

Research output: Contribution to journalArticle

Losa, M, Scavini, M, Gatti, E, Rossini, A, Madaschi, S, Formenti, I, Caumo, A, Stidley, CA & Lanzi, R 2008, 'Long-term effects of growth hormone replacement therapy on thyroid function in adults with growth hormone deficiency', Thyroid, vol. 18, no. 12, pp. 1249-1254. https://doi.org/10.1089/thy.2008.0266
Losa, Marco ; Scavini, Marina ; Gatti, Elisa ; Rossini, Alessandro ; Madaschi, Sara ; Formenti, Ilaria ; Caumo, Andrea ; Stidley, Christine A. ; Lanzi, Roberto. / Long-term effects of growth hormone replacement therapy on thyroid function in adults with growth hormone deficiency. In: Thyroid. 2008 ; Vol. 18, No. 12. pp. 1249-1254.
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abstract = "Background: Clinical studies on the effect of growth hormone (GH) on thyroid function in patients with GH deficiency are contradictory. Further, the majority of published observations are limited to the first 6-12 months of GH replacement therapy. The aim of our study was to estimate the incidence of clinically relevant hypothyroidism in a cohort of patients with adult GH deficiency (AGHD) during long-term therapy with recombinant human GH (rhGH). Methods: The study was designed as a retrospective collection of data on thyroid function in 49 AGHD patients of whom 44 (90{\%}) had multiple hormone deficiency. Thirty-seven patients (76{\%}) were on stable levothyroxine (LT4) replacement therapy (HYPO), and 12 (24{\%}) were euthyroid (EUT). Therapy with rhGH was started at a dose of 3.5 μg/kg body weight and adjusted according to insulin-like growth factor-I (IGF-I) levels. At baseline, 6 months, 12 months, and yearly thereafter we measured free triiodothyronine (fT3), free thyroxine (fT4), thyroid-stimulating hormone, and IGF-I. Study outcome was fT4 level below the normal range (9 pmol/L), irrespectively of fT3 or thyroid-stimulating hormone levels. Results: During a follow-up of 115 patient-years, mean fT4 level decreased significantly, although remaining within the normal range (p = 0.0242; month 48 vs. baseline). The largest decrease was between baseline and month 6, when fT4 decreased of 1.43 pmol/L (95{\%} confidence interval, 0.33-2.53) per 1 unit (μg/kg body weight) increase in rhGH dose. The incidence of hypothyroidism was 1.2 (HYPO group) and 6.7 (EUT group) events per 100 patient-years. Conclusion: We confirm that in patients with AGHD, rhGH therapy is associated with a small, although significant, decrement of fT4 in the first 6 months of replacement therapy. However, the incidence of hypothyroidism is low. Monitoring of thyroid function during rhGH therapy is advisable, particularly in the first year of therapy when the largest decrease in fT4 occurs.",
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AU - Losa, Marco

AU - Scavini, Marina

AU - Gatti, Elisa

AU - Rossini, Alessandro

AU - Madaschi, Sara

AU - Formenti, Ilaria

AU - Caumo, Andrea

AU - Stidley, Christine A.

AU - Lanzi, Roberto

PY - 2008/12/1

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N2 - Background: Clinical studies on the effect of growth hormone (GH) on thyroid function in patients with GH deficiency are contradictory. Further, the majority of published observations are limited to the first 6-12 months of GH replacement therapy. The aim of our study was to estimate the incidence of clinically relevant hypothyroidism in a cohort of patients with adult GH deficiency (AGHD) during long-term therapy with recombinant human GH (rhGH). Methods: The study was designed as a retrospective collection of data on thyroid function in 49 AGHD patients of whom 44 (90%) had multiple hormone deficiency. Thirty-seven patients (76%) were on stable levothyroxine (LT4) replacement therapy (HYPO), and 12 (24%) were euthyroid (EUT). Therapy with rhGH was started at a dose of 3.5 μg/kg body weight and adjusted according to insulin-like growth factor-I (IGF-I) levels. At baseline, 6 months, 12 months, and yearly thereafter we measured free triiodothyronine (fT3), free thyroxine (fT4), thyroid-stimulating hormone, and IGF-I. Study outcome was fT4 level below the normal range (9 pmol/L), irrespectively of fT3 or thyroid-stimulating hormone levels. Results: During a follow-up of 115 patient-years, mean fT4 level decreased significantly, although remaining within the normal range (p = 0.0242; month 48 vs. baseline). The largest decrease was between baseline and month 6, when fT4 decreased of 1.43 pmol/L (95% confidence interval, 0.33-2.53) per 1 unit (μg/kg body weight) increase in rhGH dose. The incidence of hypothyroidism was 1.2 (HYPO group) and 6.7 (EUT group) events per 100 patient-years. Conclusion: We confirm that in patients with AGHD, rhGH therapy is associated with a small, although significant, decrement of fT4 in the first 6 months of replacement therapy. However, the incidence of hypothyroidism is low. Monitoring of thyroid function during rhGH therapy is advisable, particularly in the first year of therapy when the largest decrease in fT4 occurs.

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