Parathyroid hormone is elevated but bone markers and density are normal in young female subjects who consume inadequate dietary calcium.

Dietary Ca and osteocalcin (OC), parathyroid hormone (PTH), 25-hydroxyvitamin D (25-OH-D), insulin-like growth factor (IGF)-I and sex hormone binding globulin (SHBG) were assessed simultaneously to bone mineral density (BMD) in 200 adolescent girls (aged 11-15 years) and 100 young women (aged 20-23 years), selected from the lowest and highest end of the Ca intake distribution of a larger population sample. Ca intake was evaluated by food frequency questionnaires, BMD was measured by dual energy x-ray absorptiometry at ultradistal and proximal radius of non-dominant arm, bone age was estimated from x-rays of left hand and wrist according to Tanner et al. (1983). Surprisingly, mean Ca intakes were below the dietary reference intakes in the subgroups of girls and women with the highest measured Ca consumption. Postmenarcheal, but not premenarcheal girls showed radial densities as high as the women and in no group was BMD associated with Ca intake. In all adolescents serum PTH was negatively related to dietary Ca. In girls before menarche IGF-I was positively associated with bone age, while in the same subjects the negative relationship between SHBG and BMD pointed to the crucial role of bioavailable sex steroids on bone mass apposition in early puberty. OC levels decreased progressively with age, while serum 25-OH-D significantly increased after menarche. In conclusion, although in adolescents low Ca intake has not been shown to induce any immediate deleterious effect on radial density, the compensatory hypersecretion of PTH supports the need for an adequate Ca intake to achieve peak bone mass.

Critical years and stages of puberty for radial bone mass apposition during adolescence.

The acquisition of radial mineral density was evaluated in relation to anthropometric characteristics, menarche status, calcium intake and physical activity in a healthy young female population (200 girls and 100 women, respectively aged 11-16 yrs and 20-24 yrs) living in an area of Southern Italy. We performed bone mineral density (BMD) by dual energy X-ray absorptiometry on the ultradistal and middistal radius. Dietary calcium intake was evaluated by a detailed Food Frequency Questionnaire and confirmed by a 3-day record. A questionnaire on energy expenditure was used to assess physical activity in each participant. Morning blood samples were drawn from fasting girls to measure 25-hydroxycalciferol (25 OH-D). We found current calcium above the levels reported by Recommended Dietary Allowances (RDA) in only 31% of women and 6% of girls. BMD steadily increased up to the age of 16 and was increased in postmenarcheal girls compared to premenarcheals of the same pubertal stage. Bone density was also significantly related to age, weight and height in postmenarcheal adolescents, while in girls before and after menarche, no relation was observed between radial BMD and calcium intake or physical activity. In the presence of comparable calcium-intake values recorded in pre- and in postmenarcheal girls, the latter subgroup displayed a marked increase of 25 OH-D serum levels. Our study revealed a calcium intake lower than the RDA in a large percentage of healthy girls and young women, and emphasized the importance of menarche occurrence in bone mass acquisition during pubertal development.

The effect of dietary calcium intake on bone mineral density in healthy adolescent girls and young women in southern Italy.

BACKGROUND: The association between forearm bone mineral areal density (BMD) and dietary calcium, anthropometric characteristics, puberty, and physical activity was studied for the first time in 200 girls (aged 11-15 years) and 100 women (aged 20-23 years) living in Southern Italy. METHODS: The BMD was assessed by dual energy x-ray absorptiometry at ultradistal (ud) and proximal (pr) radial sites and dietary calcium was evaluated using Food Frequency Questionnaires and detailed 3-day food records. RESULTS: For population samples grouped according to low and high calcium intake levels, forearm densities were quite similar among both girls and women. Independently of calcium intake, girls displayed strong correlations between ud/pr-BMD and age, bone age, weight, height and BMI. Furthermore, in girls of similar age and BMI, radial densities were substantially increased following menarche. Positive relationships between weight, BMI and both ud/pr-BMD were only evident in women with high calcium intake. CONCLUSIONS: This study showed that different calcium intake values do not appear to affect forearm mineral densities at the ages investigated, however puberty represents the major event in radial bone mass acquisition during adolescence.

GH secretion in thalassemia patients with short stature.

The physiological role of GH secretion on growth retardation remains to be elucidated especially in patients with beta-thalassemia. In the present study, we investigated IGF-1 circulating levels as well as GH release following GHRH alone or combined with some inhibitors of somatostatin: pyridostigmine and arginine. In thalassemic patients lower IGF-1 circulating levels appear to be negatively correlated with both aspartate aminotransferase and alanine aminotransferase as well as with ferritin circulating levels indicating a probable role of hepatic hemosiderosis in IGF-1 production. The authors however suggest that reduced IGF-1 secretion is not the main cause of growth retardation since this would have elicited an enhanced response of GHRH in the presence of a normal hypothalamic pituitary axis. In contrast, they noticed that GH response to GHRH when expressed as area under the curve was lower in thalassemic patients compared to controls. The combination of GHRH with either pyridostigmine or arginine induced a GH secretion in thalassemics which was comparable to that of controls. The results of this study lead to conclude that the alteration of GH secretion is due, in such patients, to an increased somatostatin activity.

Follow-up study of thyroid function in polytransfused thalassemic patients.

The aim of our investigation was to evaluate thyroid function by a follow-up study in 45 polytransfused thalassemic patients, since endocrine abnormalities are frequent consequences of iron overload in thalassemia major. Significant changes of thyroid function have been revealed in the time elapsing the observation, despite unchanged haematological parameters; at the end of the present study five patients were affected by overt hypothyroidism and 15 patients by subclinical hypothyroidism. Ultrasound thyroid volume in 13 randomly selected patients was greatly reduced, while thyroid Magnetic Resonance Imaging (MRI) was not able to detect tissue alterations. Inversely, liver MRI was markedly reduced in 14 patients and negatively related to ferritine levels (P< 0.01). We conclude that polytransfused thalassemics are frequently affected by thyroid disfunction; haepatic haemosiderosis due to iron overload seems influence hormonal peripheral metabolism, although the patients display a moderate compliance with iron chelation therapy. Therefore, periodic thyroid investigation should be carried out in thalassemic subjects in order to detect patients who need hormone replacement therapy.