Induction of puberty by pulsatile gonadotropin releasing hormone

The relationship between Insulin-like Growth Factor 1, sex steroids and timing of the pubertal growth spurt

OBJECTIVE

Progress through puberty involves a complex hormonal cascade, but the individual contributions of hormones, particularly IGF-1, are unknown. We reanalysed Chard growth study data to explore the tempo of puberty based on changes in both height and hormone levels, using a novel method of growth curve analysis.

DESIGN AND SUBJECTS

Schoolboys (n = 54) and girls (n = 70) from Chard, Somerset, England, recruited in 1981 at age 8/9 and followed to age 16.

MEASUREMENTS

Every 6 months, height and Tanner stages (genitalia, breast, pubic hair) were recorded, and in a subsample (24 boys, 27 girls), blood samples were taken. Serum IGF-1, testosterone (boys) and oestradiol (girls) were measured by radioimmunoassay. Individual growth curves for each outcome were analysed using variants of the super-imposition by translation and rotation (SITAR) method, which estimates a mean curve and subject-specific random effects corresponding to size, and age and magnitude of peak velocity.

RESULTS

The SITAR models fitted the data well, explaining 99%, 65%, 86% and 47% of variance for height, IGF-1, testosterone and oestradiol, respectively, and 69-88% for the Tanner stages. During puberty, the variables all increased steeply in value in individuals, the ages at peak velocity for the different variables being highly correlated, particularly for IGF-1 vs height (r = 0·74 for girls, 0·92 for boys).

CONCLUSIONS

IGF-1, like height, the sex steroids and Tanner stages, rises steeply in individuals during puberty, with the timings of the rises tightly synchronized within individuals. This suggests that IGF-1 may play an important role in determining the timing of puberty.

[Ovulation induction by pulsatile GnRH therapy in 2014: literature review and synthesis of current practice]

The hypogonadotropic hypogonadism is an easily treatable form of female infertility. The most common cause of hypogonadotropic hypogonadism is functional hypothalamic amenorrhea. The GnRH pump is a simple and effective treatment to restore fertility of patients with hypothalamic amenorrhea: cumulative pregnancy rate is estimated between 70 and 100% after 6 cycles, compared to a low rate of complications and multiple pregnancies. While only 2.8 cycles are on average required to achieve a pregnancy with a pump, this induction of ovulation stays underused in France. The objective of this paper is to propose a practical manual of pulsatile GnRH, in order to improve the accessibility of pulsatile GnRH for patients with hypogonadotropic hypogonadism.

Maturation of sleep-wake gonadotrophin-releasing hormone secretion across puberty in girls: potential mechanisms and relevance to the pathogenesis of polycystic ovary syndrome

Neuroendocrine mechanisms underlying the progression of sleep-wake gonadotrophin-releasing hormone (GnRH) pulse secretion across puberty have remained enigmatic. Here, the changes of sleep-wake luteinising hormone (LH) (and, by inference, GnRH) pulse secretion across puberty in normal girls are reviewed, primarily focusing on available human data. It is suggested that the primary control of GnRH pulse frequency changes across puberty, with sex steroid feedback exerting minimal control during childhood, but primary control during adulthood. A working model is proposed regarding how such a transfer of GnRH pulse frequency control may partly account for the prominent day-night differences of GnRH pulse frequency characteristic of puberty. How this model may be relevant to the genesis of abnormal GnRH secretion in peripubertal girls with hyperandrogenaemia is then described.

How do you initiate oestrogen therapy in a girl who has not undergone puberty?

The physiology of puberty needs to be taken into consideration in the induction of puberty. Puberty is a relatively slow process and replacement therapy should mimic this. Long-term maintenance requires careful monitoring and long-term assessment of risk-benefit. This has not been appreciably defined in the adolescent population. Options for fertility need careful consideration and may depend on the adequacy of pubertal induction in terms of uterine development. A number of regimens are available for pubertal induction but the lack of comparisons makes it difficult to advocate for a particular regimen. There remain a number of areas of uncertainty, and future studies need to consider these issues and whether there are cardiovascular risk factor advantages to certain preparations. The long-term risks of breast and gynaecological malignancy remain uncertain. Long-term cohort studies are required to address these issues.

Ascertainment and Treatment of Delayed Puberty

The majority of patients with pubertal delay, can be classified as having primary pubertal delay (constitutional delay of growth and puberty, CDGP), although any child with a chronic disease could present with delayed puberty. In contrast, children with hypogonadism, either hyper- or hypogonadotropic, exhibit a total absence of pubertal development. Hence, early evaluation of these patients should be performed. Delay of puberty leads to psychological problems, secondary to short stature and/or delay in the acquisition of secondary sex characteristics and the reduction of bone mass. Although the final height in patients with CDGP is usually normal, some of these patients do not reach the third percentile or remain in the lowest part of the growth chart according to familial height. The most common reason for treating CDGP patients, usually with sex steroids, is for psychological difficulties and for loss of bone mineralization. Treatment must be individualized. Therapeutic options and new drugs will be discussed. Appropriate treatment and adequate nutritional intake are indicated in patients with delayed puberty due to chronic illness. In patients with hypo- or hypergonadotropic hypogonadism, puberty must be induced or completed. Different treatments (GnRH analogues, gonadotropins and sex steroids), and the main objectives are discussed.

Central causes of hypogonadism--functional and organic

Whether caused by environmental factors, lesions, genetic mutations, drug interactions, or unknown origins, the path of the central causes of hypogonadism frequently leads back to the GnRH pulse generator. In some cases, the cause can be unequivocally traced to a single factor, such as some of the congenital syndromes previously described. In most instances, however, hypogonadism is occult or functional. Because of the wide spectrum and complexity of underlying causes, a definitive diagnosis, especially in functional causes of the disorder, is not always attainable.

Disorders of pubertal development

Puberty is the period of life during which reproductive capability is acquired. It is characterized clinically by the acquisition of secondary sexual characteristics associated with a growth spurt, and on average takes 3-4 years. Early maturation is defined as the development of sexual characteristics before the age of 8 years in girls and 9 years in boys. Delayed puberty is defined when there are no signs of puberty at the age of 13.4 years in girls and 14 years in boys (2 SD above the mean of chronological age for the onset of puberty). There are many forms of premature sexual maturation: gonadotrophin-dependent (central, or 'idiopathic' or 'true' precocious puberty) and gonadotrophin-independent precocious puberty (McCune-Albright syndrome in girls, testotoxicosis in boys); isolated premature thelarche (in the forms of classical, atypical and variant); premature adrenarche (characterized by the production of significant quantities of androgens between 5 and 8 years of age); premature menarche. The differential diagnosis of delayed puberty is between constitutional delay of growth and puberty, pubertal delay secondary to chronic disease and hypogonadotrophic hypogonadism.

Age-related changes in the regulation of luteinizing hormone secretion by estrogen in women

Despite the many studies that have been conducted using both primate and human models to understand the control of the menstrual cycle, there are many aspects of the hormonal dynamics of the menstrual cycle that are not understood. This Minireview summarizes the changes in estrogen regulation of luteinizing hormone (LH) secretion that occur throughout life in women from the time of maturation of the hypothalamic-pituitary axis resulting in the occurrence of the LH surge during puberty, through the reproductive years, to the changes in the regulation of the LH surge during premenopause and, subsequently, menopause.

Delayed puberty

Puberty is the acquisition of secondary sexual characteristics associated with a growth spurt and resulting in the attainment of reproductive function. Delayed puberty is diagnosed when there is no breast development by 13.4 years of age in a girl and no testicular enlargement by 14.0 years in a boy. The aetiologies are: (i) pubertal delay, either with constitutional delay of growth and puberty or secondary to chronic illness, and (ii) pubertal failure, with hypogonadotrophic (defect in the hypothalamo-pituitary region) or hypergonadotrophic (secondary to gonadal failure) hypogonadism, or both (secondary to radio/chemotherapy). The investigation includes: history, auxological data and pubertal development examination. Boys usually require treatment and, if they do not respond, investigation. In girls it is appropriate to measure the thyroid function and karyotype first and, if necessary, to offer treatment. If they present with dysmorphic features, or positive familial history, an assessment is required before treatment.

Mechanism of puberty

The hypothalamo-pituitary-gonadal axis in children is fully functional in fetal life and immediately after birth. The reason why it declines with advancing years of childhood is not clear but gonadotropin pulsatility is at a nadir at 6 years of age. From that time pulsatile gonadotropin starts to reappear but, again, the reason why this happens is completely unknown. All of the events of puberty can be ascribed to pulsatile gonadotropin-releasing hormone stimulation causing pulsatile gonadotropin stimulation of sex steroids. The sex steroids explain the development of the pubertal characteristics; the fact that girls have an earlier growth spurt than boys is explained by the differential effect of oestradiol and testosterone on hypothalamic control of pituitary growth hormone secretion.

Development of the hypothalamic-pituitary-ovarian axis

The onset of puberty is a centrally driven process, the detailed mechanisms of which are not known. It is translated into an increased activity of the hypothalamic GnRH pulse generator. This in turn is seen as increased pituitary pulsatile secretion of LH and FSH. LH pulses are observed even in midchildhood, particularly after the onset of sleep. Onset of puberty is associated with a greater increase in LH pulse amplitude than frequency and a much greater increase in LH and FSH. A progressive increase in daytime pulsatility occurs, with a gradual reduction of sleep-entrained amplification. Prepubertal FSH concentrations are relatively high in girls, and continous ovarian follicular growth and atresia take place, with estradiol concentrations being higher than in boys. Only after the steep early pubertal increase in LH, ovarian steroidogenesis is activated, with increases in androgen and estrogen secretion. Under further FSH stimulation, follicular growth and maturation proceed. The first menstrual cycles are mostly anovulatory for 1 to 2 years. Luteal phase insufficiency is common the first five years after menarche.

Chronobiologic evolution of luteinizing hormone secretion in adolescence: developmental patterns and speculations on the onset of the polycystic ovary syndrome

OBJECTIVE

To investigate the long-term evolution of the LH circadian profile in adolescent women with anovulatory cycles and normal or elevated LH levels in the first evaluation.

DESIGN

Prospective controlled clinical study.

SETTING

Reproductive endocrinology unit of an academic medical center.

PATIENT(S)

Twelve healthy anovulatory adolescent girls aged 12 to 17 years (5 subjects with high plasma LH level and 7 subjects with normal LH level) and four ovulatory subjects as controls.

INTERVENTION(S)

Blood samples were drawn every 20 minutes for 24 hours beginning at 10:00 A.M. at early and late gynecologic ages.

MAIN OUTCOME MEASURE(S)

Luteinizing hormone, FSH, E2, T, androstenedione, ovarian volume.

RESULT(S)

In the first evaluation, the highest plasma LH levels and greatest pulse amplitude were found early in the morning in the normal-LH group and late in the afternoon in the high-LH group. Controls did not display any significant circadian variation in LH secretion. The second evaluation revealed ovulatory cycles in six of seven subjects (85.7%) in the normal-LH group with the disappearance of the circadian rhythm. Two of five (40%) patients with high LH in the first evaluation became ovulatory with a significant decrease of mean LH levels and the disappearance of the circadian rhythm. Girls of both groups who remained anovulatory still displayed the accentuated circadian profiles that were seen at the first evaluation.

CONCLUSION(S)

An accentuated 24-hour LH periodicity is typical of puberty but disappears in adulthood. The persistence of these rhythms in persistently anovulatory adolescents may indicate a maturational arrest. In particular, the persistence of the high LH circadian profile with the highest values during the day is very similar to that found in polycystic ovary syndrome.

Sexual precocity: sex incidence and aetiology

The aetiology of 197 girls and 16 boys presenting with sexual precocity was reviewed. Ninety one girls and four boys had central precocious puberty (M:F 23:1); a cause was identified in all the boys but in only six girls. All boys with precocious puberty need detailed investigation; in girls investigation should be based on clinical findings, particularly the consonance of 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)

Growth hormone deficiency throughout puberty

Growth during puberty does not appear to be the major determinate of final height in isolated GH deficient patients. Early diagnosis and commencement of therapy are probably the most important factors, as reflected by the correlation between final height and height at the onset of puberty. The cost effectiveness of increasing the dose of GH during puberty does not appear to represent any advantage from the data presently available. Indeed, such an approach may have a deleterious effect on final height by shortening the duration of pubertal maturation. Further prospective studies are required to demonstrate the effectiveness of manipulating the onset and duration of puberty using gonadotrophin releasing hormone analogues on final height in isolated GH deficiency.

The role of treatment with growth hormone in infertile patients

The reality of the interaction of GH and its mediator, IGF-I, with gonadotrophins is now established. The results of these studies and others have obvious implications, both physiologically and clinically. Co-treatment with GH augments the gonadal response to gonadotrophins, and it seems to be of particular value in patients who are poor responders to gonadotrophin treatment and who have pituitary hypofunction induced surgically, idiopathically (hypogonadotrophic hypogonadism) or medically (treatment with GnRH analogues). There is conflicting evidence as to whether the observed effect of GH is exerted directly on the ovary or mediated through IGF-I. Treatment with GH causes a distinct increase in serum IGF-I concentrations, which correlate with, but are always higher than, follicular fluid levels, suggesting that GH stimulates hepatic production of IGF-I and that the effect on the ovary is endocrine. Further research will, hopefully, clearly define the precise therapeutic role of GH in the induction of ovulation, the selection of the most appropriate group of patients to be treated, and the minimum dose of GH needed to sensitize the ovary. Further studies are also needed to explore the action of GH and to define the role of IGF-I in the process of follicular development.

Management of constitutional delay in growt and puberty

Constitutional delay in growth and puberty is a variant of normal growth and development that can cause a significant degree of psychological disturbance in otherwise healthy children, and is most often seen in boys of pubertal age. Careful assessment is necessary to rule out other endocrine or nonendocrine diseases. In some patients, therapy with oxandrolone or testosterone may be necessary to advance growth and/or pubertal development and thereby prevent serious psychological disturbance that can persist even into adult life. In the majority, however, reassurance will usually suffice.

Isolated hypogonadotrophic hypogonadism: a family with autosomal dominant inheritance

A family is reported in which isolated hypogonadotrophic hypogonadism is inherited as an autosomal dominant condition with variable expression. In previous familial cases, inheritance was autosomal recessive. Comparison is made with the endocrine and genetic findings in Kallmann's syndrome, which should be considered a separate disorder. There is difficulty in drawing a sharp distinction between hypogonadotrophic hypogonadism and constitutional delay in puberty in this family.

Injection sites and pharmacokinetics of luteinizing hormone releasing hormone: comparison of two different subcutaneous administration routes

A normal pituitary-gonadal function is reinduced by iv or sc pulsatile LHRH therapy, administered by a portable pump. In order to evaluate the differences between different sites of injection on the LHRH bioavailability, we compared the LHRH plasma concentration after a single LHRH injection in the lower abdominal wall and in the upper arm, in 5 patients with idiopathic hypogonadotropic hypogonadism, during LHRH treatment. Our data showed no significant differences in using both administration routes. In fact, LHRH absorption (secretory area and peak value) is quite similar. However, patients tolerated LHRH administration in the abdominal wall more so than in the upper arm. Both ways of administration are effective with regards to the pituitary responsiveness but we can not forget that patients compliance is of great importance in order to obtain the best results in a long-term therapy.

Gonadotrophin, growth hormone and prolactin secretion in children with primary hypothyroidism

We have studied eight children with primary hypothyroidism (6F, 2M) aged 6.7 to 14.2 years. The girls were prepubertal and the boys had early normal pubertal development. Overnight secretion of LH, FSH, TSH, PRL and GH, and ovarian ultrasound morphology were assessed before and up to 9 months after commencing thyroxine treatment. Serum FSH concentrations in all the girls were increased above LH levels and severe hypothyroidism was associated with reduced GH secretion. These abnormalities reversed with thyroxine treatment. The boys had less severe hypothyroidism and did not demonstrate abnormal gonadotropin or GH secretion. We conclude that primary hypothyroidism in childhood is associated with widespread disturbance of pituitary function, including increased FSH secretion often without signs of early sexual maturation.