Cyclical ovarian function resistant to treatment with an analogue of luteinizing hormone releasing hormone in McCune-Albright syndrome

Peculiarities of Precocious Puberty in Boys and Girls With McCune-Albright Syndrome

McCune-Albright Syndrome (MAS; OMIM # 174800) is a rare, sporadic disease caused by a post-zygotic, activating mutation in the guanine-nucleotide binding protein α-subunit (GNAS1) gene. MAS is characterized by the clinical triad of polyostotic fibrous dysplasia of bone, café-au-lait skin pigmentation and peripheral precocious puberty. However, clinical presentation is highly variable depending on mosaic tissue distribution of mutant-bearing cells. Precocious puberty is the most common endocrine manifestation of MAS and is often the presenting, and sometimes the only, clinical sign of MAS. Due to the very low prevalence of MAS, data on course of precocious puberty, effectiveness of treatments and gonadal function during post-pubertal period are lacking. Our knowledge on this issue derives essentially from case reports and small cohorts of patients. The aim of this review is to report all available literature data on clinical aspects, therapeutic management and outcomes of precocious puberty in children with MAS. A systematic research was carried out through MEDLINE via PubMed, EMBASE, Web of Science, Semantic Scholar, Cochrane Library.

Endocrine manifestations of stimulatory G protein alpha-subunit mutations and the role of genomic imprinting

The heterotrimeric G protein G(s) couples hormone receptors (as well as other receptors) to the effector enzyme adenylyl cyclase and is therefore required for hormone-stimulated intracellular cAMP generation. Receptors activate G(s) by promoting exchange of GTP for GDP on the G(s) alpha-subunit (G(s)alpha) while an intrinsic GTPase activity of G(s)alpha that hydrolyzes bound GTP to GDP leads to deactivation. Mutations of specific G(s)alpha residues (Arg(201) or Gln(227)) that are critical for the GTPase reaction lead to constitutive activation of G(s)-coupled signaling pathways, and such somatic mutations are found in endocrine tumors, fibrous dysplasia of bone, and the McCune-Albright syndrome. Conversely, heterozygous loss-of-function mutations may lead to Albright hereditary osteodystrophy (AHO), a disease characterized by short stature, obesity, brachydactyly, sc ossifications, and mental deficits. Similar mutations are also associated with progressive osseous heteroplasia. Interestingly, paternal transmission of GNAS1 mutations leads to the AHO phenotype alone (pseudopseudohypoparathyroidism), while maternal transmission leads to AHO plus resistance to several hormones (e.g., PTH, TSH) that activate G(s) in their target tissues (pseudohypoparathyroidism type IA). Studies in G(s)alpha knockout mice demonstrate that G(s)alpha is imprinted in a tissue-specific manner, being expressed primarily from the maternal allele in some tissues (e.g., renal proximal tubule, the major site of renal PTH action), while being biallelically expressed in most other tissues. Disrupting mutations in the maternal allele lead to loss of G(s)alpha expression in proximal tubules and therefore loss of PTH action in the kidney, while mutations in the paternal allele have little effect on G(s)alpha expression or PTH action. G(s)alpha has recently been shown to be also imprinted in human pituitary glands. The G(s)alpha gene GNAS1 (as well as its murine ortholog Gnas) has at least four alternative promoters and first exons, leading to the production of alternative gene products including G(s)alpha, XLalphas (a novel G(s)alpha isoform that is expressed only from the paternal allele), and NESP55 (a chromogranin-like protein that is expressed only from the maternal allele). A fourth alternative promoter and first exon (exon 1A) located approximately 2.5 kb upstream of the G(s)alpha promoter is normally methylated on the maternal allele and transcriptionally active on the paternal allele. In patients with isolated renal resistance to PTH (pseudohypoparathyroidism type IB), the exon 1A promoter region has a paternal-specific imprinting pattern on both alleles (unmethylated, transcriptionally active), suggesting that this region is critical for the tissue-specific imprinting of G(s)alpha. The GNAS1 imprinting defect in pseudohypoparathyroidism type IB is predicted to decrease G(s)alpha expression in renal proximal tubules. Studies in G(s)alpha knockout mice also demonstrate that this gene is critical in the regulation of lipid and glucose metabolism.

In vitro production of estradiol by ovarian granulosa cells in a case of McCune-Albright syndrome

A 14-year-old girl presented with classic McCune-Albright syndrome. She underwent the ablation of several cysts during a laparotomy performed on the basis of persistent and intense pelvic pain and recurrent episodes of menometrorrhagia not responsive to pharmacologic therapy. Granulosa cells obtained from an isolated follicle and a cyst were cultured and estradiol (E2) secreted in the culture medium measured. Granulosa cells, obtained from the follicle, produced much higher levels of estradiol compared to those of cells coming both from follicles of equivalent size and preovulatory follicles of normal patients. Secretion of E2 by granulosa cells from the cyst was comparable to that of normal preovulatory follicles. We conclude that in this patient, ovaries are hyperfunctioning in terms of E2 production. This high production of estradiol and the fact that several cysts were found in the ovaries can justify the high levels of estradiol found in the serum of this patient at the moment of the operation.

Pharmacology of new hormonal therapies in the treatment of pediatric endocrine disorders

Advances in genetic engineering will make possible treatment of many pediatric endocrine disorders with replacement therapy. Some of these conditions include short stature, precocious puberty, and diabetes mellitus. Although the availability of such hormonal replacement offers new treatment modalities, an understanding of their mechanism of action and pharmacologic characteristics is crucial to maximize their effectiveness while minimizing possible untoward effects. The clinician must evaluate potential risks and benefits as these substances come to market without definitive answers being available as to their long-term effects.

Effects of cyproterone acetate, LHRH agonist and ovarian surgery in McCune-Albright syndrome with precocious puberty and galactorrhea

We have studied the endocrinological pattern in a girl with McCune-Albright syndrome. The young patient showed: normal prepubertal serum levels of gonadotropins, fluctuating estrogen concentrations, which sometimes were similar to the levels in adult women of fertile age, hyperprolactinemia with galactorrhea, ovarian cysts. The effects of treatment with antiandrogen drug, cyproterone acetate, and of a LHRH agonist, buserelin (less than D-Ser[TBU(8)6-des-gly NH2.10 greater than LHRH ethylamide), were studied. Cyproterone acetate with or without buserelin did not fully suppress estradiol concentrations. On the other hand, surgical resection of these cysts resulted in both clinical and endocrinological remission. It is likely that in this case of McCune-Albright syndrome precocious puberty was a result of ovarian estrogen secretion, while pubertal activation of the hypothalamus-pituitary axis was absent. Hyperprolactinemia, which appeared after the beginning of the combined therapy with buserelin and cyproterone acetate, was probably due to the elevated estrogen levels.

Clinical applications of LHRH analogues

What is the current state of clinical application of inhibition of gonadal activity with LHRH agonists or antagonists? It seems unlikely in the short term that antagonists will be widely applied due to the short-acting nature of the present compounds and their troublesome side-effects. In contrast clinical studies with a number of agonists have demonstrated their efficacy in producing a hypogonadal state safely with rapid recovery following cessation of therapy. Although nasal administration may be suitable for short-term suppression (up to 28 days) it seems likely that long-acting depot preparations will be useful for more prolonged suppression. Perhaps the easiest application to determine will be the profound suppression required to produce medical castration in hormone-dependent tumours. The combination of agonist and receptor blocker is attractive particularly when the receptor blocker like cyproterone acetate also suppresses the release of LH, FSH and adrenocorticotrophic hormone. In cancer of the prostate and breast the side-effects due to inhibition of secretion of testosterone and oestradiol are tolerable although the only benefit over castration is the avoidance of minor surgery. The agonists should improve significantly the existing treatment for precocious puberty, endometriosis, uterine fibroids, polycystic ovary syndrome (PCO) and induction of ovulation although large scale trials comparing different therapies and doses are required. Finally, the concept of combination therapies to block further the influence of steroid hormones suggests challenging possibilities for even more effective therapy.

Treatment of precocious puberty in the McCune-Albright syndrome with the aromatase inhibitor testolactone

The McCune-Albright syndrome is characterized by café au lait spots, fibrous dysplasia of bones, and sexual precocity. Girls with precocious puberty due to this syndrome have episodic increases in serum estrogen levels together with the formation of large ovarian cysts. The serum gonadotropin levels are typically suppressed, and the precocious puberty has not responded to treatment with long-acting analogues of luteinizing hormone-releasing hormone (LHRH). Encouraged by our initial success in a pilot study of one patient, we have now treated five girls with the McCune-Albright syndrome with the aromatase inhibitor testolactone, which blocks the synthesis of estrogens. Testolactone decreased the levels of circulating estradiol (P less than 0.05) and the ovarian volume (P less than 0.05), and there was a return to pretreatment levels after testolactone was stopped. During treatment, the peak responses of luteinizing hormone and follicle-stimulating hormone to stimulation by LHRH rose above suppressed pretreatment levels--significantly above pretreatment levels for follicle-stimulating hormone (P less than 0.02)--and then returned to pretreatment levels after testolactone was discontinued. Growth rates fell in three patients during treatment but could not be assessed in the other two because of bone deformities. The mean rate of bone maturation decreased and menses stopped in three of the four girls who were menstruating regularly. We conclude that testolactone is an effective treatment of precocious puberty in the McCune-Albright syndrome.

Autonomous ovarian hyperfunction followed by gonadotrophin-dependent puberty in McCune-Albright syndrome

A 5-year-old girl with the McCune-Albright syndrome presented with precocious puberty secondary to autonomously functioning ovarian cysts, followed by true central puberty. Progression from gonadotrophin-independent to gonadotrophin-dependent precocious puberty may occur from elevated sex steroid levels leading to the early maturation of the hypothalamic-pituitary axis.