SUN-LB051 Low Alkaline Phosphatase? Rule out Growth Hormone Deficiency.

Abstract

Background: In a child with low alkaline phosphatase (ALP), the current algorithms include screening for genetic hypophosphatasia, nutritional deficiencies, vitamin D excess, hypoparathyroidism, celiac disease, and Wilson’s disease(1). Growth hormone deficiency is not often listed in the differential diagnoses. Growth hormone is critical for longitudinal bone growth. ALP is a known marker of bone formation. Clinical Case: A 9-year-old girl with ADHD, gastroesophageal reflux, and chronic constipation presented to the endocrinology clinic for failure to thrive (weight 26thpercentile, height 11th percentile). Other symptoms included easy bruising, non-specific bone pain, and delayed loss of deciduous teeth. Adoptive parents reported recent stagnation of height and weight. Initial laboratory work-up was normal except low ALP level of 77U/L (range 184-415), low IGF 1 of 74ng/mL (-2.2 SD), and normal IGF BP3 level of 3.1 mg/dL (range 1.8-7.1). Bone age was not delayed. Repeat ALP level 4 and 5 months later was 70-80 U/L with an elevated vitamin B6 level of 102ug/dL (range 2-32.8; 1 week after discontinuation of multivitamin), which was suspicious for hypophosphatasia. Skeletal survey was non-concerning. Other screening labs including urine phosphoethanolamine, serum zinc, magnesium, and vitamin D levels were normal. On repeat clinical evaluation five months later, the patient's height and weight had plateaued. Dual-agent growth hormone stimulation testing revealed a peak growth hormone level of 7.73 ng/mL (cut-off 10ng/mL), which was strongly suggestive of growth hormone deficiency. The patient was started on recombinant growth hormone (rGH) therapy at 0.3 mg/kg/week. Two months later, ALP level increased to 205 U/L with a vitamin B6 level of 86 ug/L. ALP has remained normal for age 6 months after starting rGH therapy, with a growth velocity of 9 cm per year, and improved vitamin B6 level. Bone pains have resolved. The patient was seen by the department of genetics recently, and confirmed to not have any mutation in the ALPL gene. Conclusions: 1) A low alkaline phosphatase level in a child with short stature can be an indicator of growth hormone deficiency. 2) ALP levels improve with replacement of growth hormone and increase in growth velocity. Reference: (1) Saraff V, Högler W et al, A Diagnostic Algorithm for Children with Low Alkaline Phosphatase: Lessons Learned from Laboratory Screening for Hypophosphatasia, The Journal of Pediatrics, Vol 172, 2016, Pg 181-186 Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. s presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.