Endocrine Abstracts

Growth Hormone (GH) deficiency in the adult is associated with sub-optimal bone mineral density (BMD) and reduced bone turnover. GH replacement therapy results in increased bone turnover and new bone formation with biphasic changes in BMD: We report a case in which the anabolic effects of GH on bone precipitated profound Vitamin D (Vit D) deficiency.

The patient 56-year-old man with panhypopituitarism following treatment for acromegaly commenced adult GH replacement following confirmation of severe GH deficiency (GHD). Baseline IGF-1 was markedly reduced at 0 nmol/L. BMD was shown severe osteoporosis at lumbar spine and hip, respectively, while bone turnover markers were normal, with urine deoxypyrodinoline cross links/creatinine (DPD/Cr) ratio of 3.2-nmol/mmol (2.3-5.4) and plasma osteocalcin 3.0 mcg/L (1-7.2). Bone profile was in normal range. GH replacement increased bone turnover, DPD/Cr ratio and plasma osteocalcin increasing to 9.6 nmol/mmol and 8.3 mcg/L respectively within 5 months, associated with increased IGF-1 (-0.92 SDS). However, 11 months after commencing GH bone turnover remained high and the patient developed symptoms of proximal myopapthy. Subsequent examination 15 months after initiation of GH revealed wasting and weakness of proximal muscles. iCa2+ and phosphate were reduced at 1.11mmol/L (NR 1.19-1.37) and 0.5 mmol/L (NR 0.8-1.44) respectively. Alkaline phosphatase (ALP) was elevated at 247 u/L (NR 35-120). Parathyroid hormone (PTH) was elevated at 558ng/L (NR 10-65). 25 (OH) cholecalciferol was reduced at <5 nmol/L (NR 10-75), while total Vit D was in the lower normal range at 23 nmol/L (NR 15-75). The patient was treated with high dose vit D analogues, with gradual improvement in symptoms and biochemistry.

This case highlights the potential for GH replacement to increase bone turnover and unmask occult Vit D deficiency in susceptible individuals. Care should be taken to optimise Vit D status in such individuals prior to and at initiation of GH.