Endocrine Abstracts

BACKGROUND: AGHD is associated with reduced BMD. GHR results in improvement in BMD, however, some patients remain osteopaenic despite all appropriate pituitary hormone replacement. PTH plays an important role in bone metabolism, with anabolic effects following intermittent administration. To date the difference in PTH activity and phosphocalcium metabolism between fully replaced AGHD patients with normal and reduced BMD has not been investigated.
OBJECTIVES: To determine the difference in PTH and phosphocalcium metabolism in AGHD patients who have normal and reduced BMD; and are adequately replaced and stable on all pituitary hormones.
METHODS: 18 AGHD patients (8 with normal BMD (mean(plus/minus SEM) femoral T-score 0.88plus/minus0.40), 10 with reduced BMD (mean(plus/minus SEM) femoral T-score -1.42plus/minus0.32)), were consented to the study. All patients were adequately GHR for at least 2 years (IGF-1 maintained within 2 standard deviations of the age-related reference range). Patients were admitted for 24 hours and half-hourly blood and 3-hourly urine samples were collected for PTH (picamoles per litre), calcium (millimoles per litre), phosphate (millimoles per litre) and nephrogenous cAMP (NcAMP, nanomoles per litre GFR). All results are expressed as mean plus/minus SEM. Local Ethical Committee approval was obtained.
RESULTS: There was no significant difference in age, gender, length of disease or duration of GHR between the 2 groups. The osteopaenic group demonstrated significantly lower 24-hour mean PTH concentration (3.55plus/minus0.15 versus 4.52plus/minus0.18, p less than 0.001), NcAMP (21.9plus/minus2.28 versus 32.7plus/minus2.91, p=0.004) and serum adjusted calcium concentration (2.35plus/minus0.004 versus 2.37plus/minus0.005, p=0.001) and higher serum phosphate concentration (1.15plus/minus0.01 versus 1.12plus/minus0.01, p=0.03). There was no significant difference in urinary calcium or phosphate excretion between the 2 groups.
CONCLUSIONS: Fully replaced AGHD patients with reduced BMD exhibit lower levels of PTH, compared with normal BMD patients and our data suggests that osteopaenia in GH-treated AGHD patients may be a result of reduced PTH activity.