Delayed puberty is commonly reported among children with SCA. We aimed to have an overview of pubertal development of children with SCA in our setting compared with healthy controls. In addition, we searched for clinical and biological factors which may expose to delayed puberty for this specific population. This study highlights delayed onset of puberty in children with SCA compared to controls. Some severity criteria such as recurrent infections and low hemoglobin levels increase the risk for delayed puberty.
We included SCA patients followed up in a reference center, but they were not representative of all children with SCA in Cameroon. However, our results give relevant data about pubertal development in patients with this condition.
In our study, 27.3% of girls and 10% of boys with SCA presented a delayed onset of puberty. A previous study in Cameroon in 2014 reported similar results[7]. But this result is lower than proportions reported in previous studies around the world. It varies from 37% to 50% for girls and 28.57–73 % for boys[8][6]. These differences could be explained by the smaller size of their study populations. On the other hand, their study groups included adolescents and young adults who were older than our subjects. This fact may have increased the probability to have a greater proportion of delayed puberty with respect to age groups.
According to literature, many mechanisms are described for delayed puberty during SCA. Chronic hypoxia related to recurrent vaso-occlusive events and chronic anemia lead to hypoplasia of pituitary gland and gonads[3]. On the other hand, iron overload secondary to hemolysis and multiple transfusions also affects the gonadotropic axis[9][10]. Micronutrient deficiency is also mentioned by some authors as part of pathogenesis of delayed puberty. Zemel et al. in 2002 found an improvement in weight and height in prepubertal children after zinc supplementation[11]. Since weight is a determining factor in the onset of puberty, zinc intake may be a protective factor in delayed puberty.
Many factors could explain delayed puberty in our study population. Firstly, SCA children had median hemoglobin level of 7.4g/dl which suggest a state of chronic hypoxia. Moreover, their values of leukocytes and thrombocytes revealed a state of blood hyperviscosity which increase the risk of vaso-occlusive crises. Then, they had high levels of bilirubin and LDH which are markers of hemolysis.
Puberty among girls
At the onset of puberty, girls with SCA were older than controls with a gap of 0.7 years. Soliman et al in Egypt and M’Pemba Loufoua in Congo also found a gap of respectively 1.8 and 2 years at stage B2 between SCA subjects and controls[8][12]. The median age of female SCA cases at the onset of puberty was 11.6 years in our study. In contrast, Komba et al in 2015 found a median age of 8.89 years in Cameroonian girls[13]. This delayed onset of puberty in girls with SCA may be due to the deleterious effects of hypoxia and chronic hemolysis on the hypothalamo-pituitary-gonadal axis[3].
The median age of menarche was 14.5 years for girls with SCA compared with 12 years for controls. Whereas the median age of menarche reported by Pasquet et al was 13.18 years in Cameroon for healthy girls[14]. Soliman et al also reported that menarche was delayed by 2.2 years in their cohort of SCA subjects[12]. Our results show a delayed onset of menses in cases compared to controls. This could be explained by low weight and BMI identified in SCA patients compared with controls in our study. The notion of target weight is described in literature as the determining factor for menarche in girls[15].Since girls with SCA are more likely to have delayed growth, they will reach the target weight needed for menarche later than healthy children. Serjeant et al in 2001 found that weight status was a predictive factor for the age of menarche in their cohort [4].
In our study group, hormone levels were within the normal range at each Tanner stage. This result was different from hypogonadism usually reported in adolescents with SCA.
Puberty among boys
Boys with SCA were older than controls at the onset of puberty with a gap of 1.7 years. Our findings are close to the 2.2-year gap reported by M’Pemba Loufoua et al in 2001. The median age of boys with SCA at the onset of puberty (stage G2) was 13 years in our study. Whereas, Komba et al found a median age of 9.63 years in healthy boys in the urban population of Cameroon [13]. Our results reflect delayed onset of puberty among boys with SCA compared to controls and urban population in Cameroon. This delay can be explained by recurrent vaso-occlusive crises which lead to hemolysis and chronic anemia. Moreover, multiple blood transfusions and chronic hemolysis may induce iron overload which is toxic for the pituitary gland and gonads[10]. Low hemoglobin levels, high bilirubin levels and LDH levels in our study population suggest a high tendency for hemolysis. At the onset of puberty, gonadotropins levels of cases were lower than values of controls. Moreover, AMH levels were higher in cases at G3 Tanner staging. AMH levels usually decrease when testosterone production increases during puberty. This increase of AMH level in SCA may be explained by hypogonadism which is mostly found among boys with SCA [3][12]. This suggests importance of long-term follow-up of these boys to look after fertility features.
Clinical and biological factors associated with pubertal development in Sickle Cell Anemia
Boys with SCA more often had delayed testicular development associated with a past history of blood transfusion (OR = 4) and severe infection (OR = 13). This association was statistically significant in case of severe infection (p = 0.03). Ozen et al in 2012 didn’t find an association between the occurrence of an endocrine complication and the severity criteria of sickle cell disease [4].
Biological parameters such as a hemoglobin F of less than 10%, a hemoglobin level of less than 7 g / dl (OR = 3.7) and leukocytes greater than 10,000 cells per mm3 (OR = 9) were associated with delayed testicular development. This association was statistically significant for hemoglobin F (p = 0.02) and leukocytes (p = 0.03). M’Pemba Loufoua et al found association between hemoglobin levels below 7 g / dl in SCA boys and delayed puberty. This may suggest that anemia is a deleterious factor for testicular development. Silva et al found an association between leukocytosis and the occurrence of chronic complications such as delayed puberty [2].
Girls with SCA and history of acute chest syndrome were 2.8 times more likely to have delayed breast development. This association was not statistically significant. This could be explained by the fact that acute chest syndrome induces hypoxia by hypoventilation [14]. This could disrupt tissue oxygen uptake in the pituitary gland and gonads. This would lead to hypogonadism with a slowing down of pubertal maturation[3].
Biological parameters such as a percentage of hemoglobin F less than 10% (OR = 2.2) and hemoglobin level less than 7 g / dl (OR = 1.4) exposed to delayed breast development among girls. Despite the fact that this finding was not statistically significant, hemoglobin F greater than 10% is a protective factor for vaso-occlusive crises[3]. Thus, a value lower than 10% can promote episodes of hypoxia, deleterious for gonadotropic axis. The use of hydroxyurea in eligible patients improves the concentration of hemoglobin F. Furthermore, a low hemoglobin level exposes the patient to high transfusion requirements. This can lead to an iron overload, which is toxic for gonadal cells[10]. The practice of exchange transfusions increases basic hemoglobin level and therefore improves tissue perfusion[17].