Recambio óseo en nodrizas adolescentes: evaluación al término de la gestación, lactancia y postdestete / Bone turnover in lactating teenagers: assessment at the end of pregnancy during and after the breast feeding period

ABSTRACT

Background: There is paucity of information about bone metabolism during pregnancy or breast feeding in teenagers. Aim: To study bone turnover at the end of pregnancy and during breast feeding in teenagers and correlate it with environmental, hormonal or nutritional variables. Subjects and methods: Thirty teenagers during their breast feeding period after a first pregnancy and 30 nulliparous girls matched for age, age of menarche and body mass index were assessed three weeks after delivery (period 1), at six months of breast feeding (period 2) and one year after the lactating period (period 3). Calcium intake and plasma calcium, phosphorus, alkaline phosphatases, parathormone, estradiol and prolactin were measured. Calcium, creatinine and hydroxyproline were also measured in a morning urine sample. Results: Lactating and control girls were aged 16.3ñ0.8 and 16.1ñ0.7 years old respectively. Calcium intake in lactating and control girls was 798ñ421 and 640ñ346 g/day respectively in period 1, 612ñ352 and 592ñ309 mg/day in period 2 and 495ñ180 and 456ñ157 g/day in period 3. During periods 1 and 2, lactating girls had higher alkaline phosphatases (161ñ37 compared to 119ñ28 U/l and 149ñ37 compared to 106ñ23 U/l), parathormone (4.3ñ2.6 compared to 2.8ñ0.8 ng/dl and 3.6ñ1.6 compared to 3.0ñ0.9 ng/dl) and urinary hydroxyproline (95ñ16 compared to 63ñ15 mg/g creatinine and 84ñ19 compared to 59ñ15 mg/g creatinine). No differences were observed in period 3. No correlation between bone turnover variables, body mass index or hormonal parameters, was observed. Conclusions: In teenagers, there is an increase in bone turnover at the end of pregnancy, that persists during the lactating period. These changes are not related to nutritional or hormonal variables