Effects of testosterone therapy for pubertal delay

Hypogonadism in Male Infants and Adolescents: New Androgen Formulations

BACKGROUND

Male hypogonadism may be associated with micropenis and cryptorchidism in newborn, absent or incomplete pubertal development when it occurs during childhood. During puberty, androgen replacement therapy plays a pivotal role in subjects with hypogonadism to induce sexual maturation, growth acceleration, anabolic effects on fat-free mass growth increasing muscle strength, directly and indirectly on the attainment of peak bone mass in young men. Moreover, in newborns with congenital hypogonadism, androgen therapy could be effective to increase genital size.

SUMMARY

Testosterone replacement therapy (TRT) represents the cornerstone of the management of hypogonadism in boys. During puberty, replacement therapy needs to be modulated with gradual dosing increase to better mimic the physiologic pubertal development. Currently, intramuscular testosterone (T) esters (in particular testosterone enanthate) and subcutaneous T pellets are the only formulations approved by the US Food and Drug Administration for delayed puberty, while no preparation is approved for long-term use in the adolescent age. Several new T formulations (as transdermal, nasal, subcutaneous, and oral formulation) are recently developed to improve the pharmacokinetic profile and to ease the administration route increasing patient compliance in adult males with hypogonadism. All these formulations are not approved for pediatric age, although some of them are used as "off-label" regimens. This special issue is aimed to illustrate new T formulations and their potential role as replacement therapy in the pediatric population, as well as to highlight investigational areas to contribute to health care improvement in these patients.

KEY MESSAGES

Despite the lack of evidence-based guidelines regarding the choice of T formulation in the pediatric population, new formulations appear to have a potential role for TRT in adolescent age. They have been designed for adult age with a little flexibility of dosage, although a few formulations may be attractive for pubertal induction and penile enlargement thanks to their greater flexibility and easing of administration. On the other hand, long-acting and stable formulations could meet post-pubertal needs, increasing TRT compliance in a critical phase as the adolescent age. Further controlled, long-term safety, and efficacy studies for all these new T formulations within the pediatric population are needed.

Testosterone Use in Adolescent Males: Current Practice and Unmet Needs

Testosterone replacement therapy (TRT) is routinely prescribed in adolescent males with constitutional delay of growth and puberty (CDGP) or hypogonadism. With many new testosterone (T) formulations entering the market targeted for adults, we review current evidence and TRT options for adolescents and identify areas of unmet needs. We searched PubMed for articles (in English) on testosterone therapy, androgens, adolescence, and puberty in humans. The results indicate that short-term use of  T enanthate (TE) or oral  T undecanoate is safe and effective in inducing puberty and increasing growth in males with CDGP. Reassuring evidence is emerging on the use of transdermal  T to induce and maintain puberty. The long-term safety and efficacy of TRT for puberty completion and maintenance have not been established. Current  TRT regimens are based on consensus and expert opinion, but evidence-based guidelines are lacking. Limited guidance exists on when and how  T should be administered and optimal strategies for monitoring therapy once it is initiated. Only  TE and  T pellets are US Food and Drug Administration approved for use in adolescent males in the United States. Despite the introduction of a wide variety of new  T formulations, they are designed for adults, and their metered doses are difficult to titrate in adolescents. In conclusion, TRT in adolescent males is hindered by lack of long-term safety and efficacy data and limited options approved for use in this population. Additional research is needed to identify the route, dose, duration, and optimal timing for TRT in adolescents requiring androgen therapy.

An approach to constitutional delay of growth and puberty

Constitutional delay of growth and puberty is a transient state of hypogonadotropic hypogonadism associated with prolongation of childhood phase of growth, delayed skeletal maturation, delayed and attenuated pubertal growth spurt, and relatively low insulin-like growth factor-1 secretion. In a considerable number of cases, the final adult height (Ht) does not reach the mid-parental or the predicted adult Ht for the individual, with some degree of disproportionately short trunk. In the pre-pubertal male, testosterone (T) replacement therapy can be used to induce pubertal development, accelerate growth and relieve the psychosocial complaints of the adolescents. However, some issues in the management are still unresolved. These include type, optimal timing, dose and duration of sex steroid treatment and the possible use of adjunctive or alternate therapy including: oxandrolone, aromatase inhibitors and human growth hormone.

Dihydrotestosterone stimulates amino acid uptake and the expression of LAT2 in mouse skeletal muscle fibres through an ERK1/2-dependent mechanism

Dihydrotestosterone (DHT) has acute/non-genomic actions in adult mammalian skeletal muscles whose physiological functions are still poorly understood. Therefore, the primary aim of this study was to investigate the acute/non-genomic effects of DHT on amino acid uptake as well as the cellular signal transduction events underlying these actions in mouse fast- and slow-twitch skeletal muscle fibre bundles. 14C-Labelled amino acids were used to investigate the effects of DHT and testosterone (T) on amino acid uptake and pharmacological interventions were used to determine the cellular signal transduction events mediating these actions. While T had no effect on the uptake of isoleucine (Ile) and α-methylaminoisobutyric acid (MeAIB) in both fibre types, DHT increased their uptake in the fast-twitch fibre bundles. This effect was reversed by inhibitors of protein translation, the epidermal growth factor receptor (EGFR), system A, system L, mTOR and MEK. However, it was relatively insensitive to inhibitors of transcription, androgen receptors and PI3K/Akt. Additionally, DHT treatment increased the expression of LAT2 and the phosphorylation of the EGFR in the fast-twitch fibre bundles and that of ERK1/2, RSK1/2 and ATF2 in both fibre types. Also, it decreased the phosphorylation of eEF2 and increased the incorporation of Ile into proteins in both fibre types. Most of these effects were reversed by EGFR and MEK inhibitors. From these findings we suggest that another physiological function of the acute/non-genomic actions of DHT in isolated mammalian skeletal muscle fibres is to stimulate amino acid uptake. This effect is mediated through the EGFR and involves the activation of the MAPK pathway and an increase in LAT2 expression.

Oral treatment for constitutional delay of growth and puberty in boys: a randomised trial of an anabolic steroid or testosterone undecanoate

Thirty three boys (mean 14.6 years old, range 12.8-16.2 years) with constitutional delay of growth and puberty were randomised into two groups to determine which form of oral treatment would give the better anthropometric response. The two drugs were administered by mouth (one tablet/day) for a mean of 3.5 months (range 3-7 months). At randomisation, 17 boys received testosterone undecanoate (40 mg/day) and 16 oxandrolone (2.5 mg/day). At the start of treatment they were prepubertal or in early puberty, their height SD score was -1.97 in boys treated with testosterone and -2.21 in those treated with oxandrolone, and their growth rates were 4.3 and 4.2 cm/year respectively. Both sex steroid and anabolic steroid treatments induced a significant growth acceleration in all patients except four (three treated with testosterone and one with oxandrolone). When treated with the alternative sex steroid, all four non-responders had a significant anthropometric response. In all boys the induced growth acceleration was sustained when treatment was interrupted. There was no significant difference in the induced growth spurt and bone maturation between the two groups. Spontaneous progress into puberty was achieved in all boys with an increase in testicular volume from a mean of 4.6 to 8.5 ml. The rate of development in secondary sexual characteristics was also similar in the two groups. These data suggest that oral testosterone and oxandrolone are equally effective in the treatment of growth delay in boys with constitutional delay of growth and puberty.

Does constitutional delayed puberty cause segmental disproportion and short stature?

We have reviewed the growth of 98 boys and 34 girls with constitutional delay of growth and puberty followed until final height. At presentation chronological age was 14.1 (1.3) years (SD) in the boys and 13.0 (1.3) years in the girls. At presentation all patients were either prepubertal or in early pubertal maturation (4 ml testicular volume in the boys and breast stage II in the girls). Twenty-nine boys (30%) and 2 girls (6%) were treated with either sex or anabolic steroids. Mean height SDS in the boys at presentation was -2.7 (0.7) which rose to -1.9 (0.9) at final height attainment. This was significantly lower than the predicted final height SDS of -1.4 (0.8) and mid-parental height SDS of -0.5 (0.7). Similar results were obtained for the girls with a height SDS at presentation of -3.2 (0.8) which increased to -2.3 (0.7) at final height which was significantly lower than predicted final height SDS of -1.7 (0.6) and mid-parental height SDS of -0.8 (0.8). Both sexes had a relatively short sitting height at presentation; sitting height SDS -3.4 (1.0) and subischial leg length SDS -2.2 (1.0) in the boys and sitting height SDS -3.6 (1.1) and subischial leg length SDS -2.5 (0.7) in the girls. The relative disproportion between the segments had no significant change at final height. We are unable to explain the failure to achieve final height potential and the relatively disproportionate stature. Our data suggest that the late timing of the onset of puberty may be deleterious to spinal growth and consequently final height.(ABSTRACT TRUNCATED AT 250 WORDS)

Is testosterone therapy for boys with constitutional delay of growth and puberty associated with impaired final height and suppression of the hypothalamo-pituitary-gonadal axis?

We report the treatment of 44 boys with constitutional delay of growth and puberty (CDGP) at a mean chronological age of 14.3 years (range, 12.4-17.1) and bone age of 12.1 years (range, 9.1-15.0). All were below the 3rd height percentile for chronological age. They received monthly intramuscular injections of depot testosterone esters (50 mg) for a mean period of 0.35 years (range, 0.25-0.5). Means (SD) height velocity was 4.5 (1.5) cm/year during a pretreatment period of 0.5 years. During a period of 0.9 years which included the period of treatment with depot testosterone, mean growth velocity increased to 8.8 (1.9) cm/year (P less than 0.001). In the initial 1.8 years following the cessation of treatment growth velocity was sustained at 7.0 (1.7) cm/year. Pretreatment height standard deviation score (SDS) for bone age was -0.89 and this gradually reduced over the next 1.5 years to a minimum of -1.48. Thereafter, height SDS for bone age gradually increased to attain a value of -1.2, 3 years after the commencement of therapy (P less than 0.02). The same pattern of an initial decrease, followed by an increase, in height prediction was also observed when TW2 height prediction was analysed. Sexual maturation progressed during treatment, with mean testicular volume increasing both during and after treatment, confirming the diagnosis of CDGP. The time interval for progress through puberty was shorter in boys with testosterone therapy than in the normal population. The mean duration of puberty was 2.2 years compared to 3.3 years in normal boys. We conclude that low-dose depot testosterone treatment is safe and effective for boys with CDGP.(ABSTRACT TRUNCATED AT 250 WORDS)

Depot testosterone in boys with anorchia or gonadotrophin deficiency: effect on growth rate and adult height

Eleven teenage boys with bilateral anorchia and 12 with gonadotrophin deficiency were treated by injections of testosterone ester (enanthate) at an initial dose of 100 mg every six to eight weeks, rising to 250 mg every four weeks after three to four years. In the anorchic boys average adult height was 177.1 cm, compared with a mean mid-parental height of 174.4 cm, and mean predicted adult heights of 177.0 cm (Tanner-Whitehouse method) and 178.0 cm (Bayley-Pinneau method). In the patients with gonadotrophin deficiency, mean adult height was 176.9 cm, compared with a mean mid-parental height of 176.1 cm, and mean predicted adults heights of 174.0 cm (Tanner-Whitehouse method) and 177.3 cm (Bayley-Pinneau method). We conclude that this testosterone regimen allows achievement of full growth potential in such patients.