Hypersecretion of hypothalamic releasing hormones: a possible explanation of the endocrine manifestations of polyostotic fibrous dysplasia (Albright's syndrome)

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.

Precocious puberty

Puberty occurring before the age of 8 years in girls and 9 years in boys in considered precocious. The numerous causes of precocity can be classified as central or peripheral. Central or true precocious puberty (CPP) is due to premature activation of the hypothalamopituitary-gonadal axis and is isosexual. Peripheral or pseudoprecocious puberty (PPP) results from the production of sex steroids independent of the H-P-G axis and may be isosexual or heterosexual. CPP is the most common form of precocity involving more than 50% of children and is much more common in girls than boys. CPP is more common between 4 and 8 years. A peak serum LH levels > 10 iu/l following GnRH stimulation is the absolute evidence of CPP. Serum IGF-I levels are predictive of the outcome. Availability of CT and MRI has helped to determine the cause of CPP in most cases. Hypothalamic hamartoma is the most common tumour causing CPP especially in boys. Adrenal causes, particularly CAH, are the commonest cause of PPP in boys whereas ovarian causes are more likely in girls. Long acting GnRH analogues provide a safe and effective form of treatment of CPP.

Acromegaly and hyperprolactinemia in a patient with polyostotic fibrous dysplasia: dynamic endocrine studies and treatment with the somatostatin analogue octreotide

Acromegaly and hyperprolactinemia have been described in association with polyostotic fibrous dysplasia; the pathogenetic mechanisms involved in the development of the endocrinopathies is unknown. We report a 26-year-old man with polyostotic fibrous dysplasia and hypersecretion of GH and PRL. Plasma GH, PRL, and insulin-like growth factor-I (IGF-I) were elevated. Glucose-non-suppressible plasma GH concentrations, GH responsiveness to TRH and GHRH, and GH suppression after a test-dose of somatostatin, octreotide, and bromocriptine were found. Plasma GHRH levels were within the normal range (< 25 ng/l). Computed tomography of the sella turcica and visual fields were normal. [111In-DTPA-D-Phe1]-octreotide scintigraphy were used to localize a possible tumor; no radioactivity was visualized at the site of the hypothalamus, the pituitary or elsewhere in the body but a considerable accumulation of radioactivity was found in the os frontalis. Therapy with octreotide by continuous sc infusion partially suppressed GH and IGF-I (and normalized PRL). The results suggest that hypersecretion of GH in our patient is not due to a GH-secreting pituitary tumor, eutopic or ectopic hypersecretion of GHRH or autonomous somatotroph function. The origin of the disease in this patient might be an abnormal hypothalamic regulation of somatotrophs and/or an alteration in the transmembrane signalling systems.

Findings on magnetic resonance imaging of the spine and femur in a case of McCune-Albright syndrome

Polyostotic fibrous dysplasia, a major osseous change in McCune-Albright syndrome, is seen in the cranium, facial bones, bones of the extremities, and ribs, but rarely in the spine. Spinal X-rays revealed no abnormalities in an 8-year-old girl with this syndrome, but 99mTc-methylene diphosphonate bone scintigraphy disclosed high-density areas in the thoracic and lumbar vertebrae. Multiple well-circumscribed areas of low signal intensity were seen on T1-weighted magnetic resonance imaging (MRI) of the spine. Although MRI spine scans in this disease have never been reported, our findings in this case proved interesting for evaluating osseous lesions. MRI made it possible to differentiate between fibrous lesions (low signal intensity on T1- and T2-weighted MRI) and cartilaginous lesions (low signal intensity on T1-weighted MRI and high signal intensity on T2-weighted MRI).

Monozygotic twins discordant for the major signs of McCune-Albright syndrome

We describe a girl, one of monozygotic (MZ) twins, with endocrine dysfunction with precocious puberty, café-au-lait nevi and polyostotic fibrous dysplasia (PFD), McCune-Albright syndrome (MAS). After treatment with cyproterone acetate for 7 years the precocious puberty and excess growth improved but the bone-age still remain advanced. The co-twin had an advanced bone-age and a small café-au-lait spot, but showed neither endocrinopathy nor fibrous dysplasia of bone. On the basis of the findings in these twins, together with those in previously reported familial cases of MAS, including two pairs of MZ twins, a 2-hit mutation hypothesis is proposed: a dominant mutation may be inherited and leads to PFD in offspring as the primary defect of MAS; the second mutation may occur in somatic cell leading to mosaicism and thus resulting in MAS. This concept explains not only sporadic cases of MAS but also reported familial cases. If we assume that the second mutation occurred in an early somatic division, it would explain the discrepancy of clinical manifestation between MZ twins.

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.

Hormone-producing tumors of the ovary

The ovary is an endocrine organ that gives rise to a wide variety of neoplastic and tumorlike nonneoplastic conditions, some of which are associated with endocrine activity. The hormones produced may be steroidal or nonsteroidal. The ovary is unique among endocrine organs in reacting to the presence of nonendocrine tumors within it by abnormal or inappropriate production of sex steroidal hormones. A classification of hormone-producing ovarian lesions is proposed based on the World Health Organization's histologicai typing of ovarian tumors.

Acromegaly, multinodular goiter and silent polyostotic fibrous dysplasia. A variant of the McCune-Albright syndrome

A 36-year-old woman is reported with a possible variant of the McCune-Albright syndrome. The triad was incomplete because of the absence of skin pigmentation and since the sexual precocity was not evident. The presence of a pituitary mass and the secretory dynamics of growth hormone and prolactin were suggestive of a mammosomatotroph cell adenoma. A toxic multinodular goiter was also associated, but unique was the spontaneous normalization of the thyroid function. Unusual was the silent evolution of the polyostotic fibrous dysplasia, which was only fortuitously discovered during magnetic resonance imaging of the pituitary region. Treatment of the acromegaly with the long-acting somatostatin analogue octreotide resulted in an important inhibition of the GH secretion and in a reduction of the volume of the pituitary adenoma.

The hyperthyroidism of polyostotic fibrous dysplasia--a possible autoimmune aetiology

Endocrine disorders are a relatively common accompaniment of polyostotic fibrous dysplasia. Considerable debate has taken place concerning possible responsible mechanisms. This case demonstrates that the hyperthyroidism associated with the condition is of thyroidal origin and of probable autoimmune aetiology.

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.

McCune-Albright syndrome with gigantism and hyperprolactinemia

We describe the case of a 38-year-old man with typical Mc Cune-Albright syndrome and the unusual combination of both growth-hormone and prolactin hypersecretion. The patient was extremely tall, which is unusual in Mc Cune-Albright syndrome, suggesting that he did not have precocious fusion of the epiphysis, a common finding in this syndrome. Unfortunately the patient refused any treatment for his disease. A similar case has been previously described only in a 14-year-old boy.

The McCune-Albright syndrome: a lethal gene surviving by mosaicism

In the McCune-Albright syndrome, fibrous dysplasia of bones and various forms of endocrine dysfunction are associated with multiple pigmented skin lesions. Examination of a 4-year-old female patient and comparison with photographs published in the literature revealed that the cutaneous pigmentation is arranged in a systematized pattern following the lines of Blaschko. Apparently, this pattern visualizes the dorso-ventral outgrowth of two different populations of cells during early embryogenesis. As all cases of the syndrome are sporadic, it is postulated that the disease is caused by an autosomal "dominant" lethal gene, leading to loss of the zygote in utero. Cells bearing the mutation can only survive when they are intermingled with normal cells. The mosaic may arise either from a gametic half chromatid mutation, or from an early somatic mutation. This concept offers an explanation for the scattered asymmetric distribution of bone lesions, and for the observation that the endocrinopathy may be either of central or peripheral origin, according to the random distribution of the mutant population of cells.

Occurrence of pituitary adenoma in craniofacial fibrous dysplasia: a neuroendocrine and neuroradiological case study

An 18 year old man with fibrous dysplasia of bone and several endocrine abnormalities was investigated. Laboratory tests showed high levels of prolactin, TSH and GH and low levels of testosterone and LH. TRH and GnRH showed normal responsiveness of the pituitary in spite of the high hormonal levels. The circadian rhythms disclosed no abnormalities of hypothalamic control. The neuroradiological study revealed pathological tissue but no positive sign of a pituitary adenoma, although the sella turcica polytomograms did suggest erosion of the floor. Our data are compatible with the presence of a mixed adenoma or adenomas of the pituitary. We emphasize the importance of a correct study, including neuroradiological and neuroendocrine investigations, in patients with fibrous dysplasia of bone.

Fibro-osseous lesions of the jaws

During the 15 years since the author's 1970 paper on fibro-osseous lesions of the jaws, the subject has continued to interest the clinician and pathologist. Several new entities have been delineated during this period, and new concepts and controversies regarding the diagnosis and management of these lesions have arisen. A classification of fibro-osseous jaw lesions that the author has found to be workable is presented, and criteria for their diagnosis and management based on the authors' experience is discussed.

Polyostotic fibrous dysplasia with acromegaly

A 26-year-old man was found to have incomplete polyostotic fibrous dysplasia of bone and elevated growth hormone and prolactin levels. There was roentgenographic evidence of a pituitary tumor. The natural history of fibrous dysplasia in relationship to excess growth hormone secretion since childhood is described.

Albright's syndrome with reactivation of fibrous dysplasia secondary to pituitary adenoma and further complicated by osteogenic sarcoma. Report of a case

To our knowledge, this is the only reported case of Albright's syndrome with reactivation of the fibrous dysplasia in adulthood, a marked elevation of growth hormone secondary to a pituitary adenoma, and development of osteosarcoma within the reactivated fibrous dysplasia. In addition, this patient also had hyperthyroidism with normal TSH levels, indicating the presence of two separate endocrinopathies. Reactivation of the fibrous dysplasia after years of arrested growth in this patient is good evidence that fibrous dysplasia does not "burn out" after adolescence but that growth ceases only when growth hormone declines to adult levels.

Mammosomatotroph hyperplasia associated with acromegaly and hyperprolactinemia in a patient with the McCune-Albright syndrome. A histologic, immunocytologic and ultrastructural study of the surgically-removed adenohypophysis

An 11-year-old girl, with the McCune-Albright syndrome, exhibited fibrous dysplasia of several bones, skin pigmentation, precocious puberty, growth hormone hypersecretion, acromegaly and hyper-prolactinemia. Histologic, immunocytologic and ultrastructural investigation of the surgically-removed pituitary showed massive mammosomatotroph hyperplasia. Since no adenoma was found, the abundance of these bihormonal cells, capable of producing both growth hormone and prolactin, was implicated in the causation of growth hormone and prolactin excess. Somatoliberin overproduction and/or somatostatin and dopamine deficiency could not account for the hypophysial abnormality, since changes in secretory rates of these hypothalamic hormones would lead to proliferation of mature somatotrophs and lactotrophs, rather than mammosomatotrophs. In our patient, a congenital hypothalamic malfunction might have been accompanied by hypersecretion of an unidentified releasing factor, resulting in pathologic differentiation of the pituitary and mammosomatotroph hyperplasia. Alternatively, mammosomatotroph hyperplasia may have been due to an inherent genetic or embryonic defect affecting primarily the pituitary. According to this interpretation, the pituitary lesion represented yet another developmental error in the setting of the McCune-Albright syndrome.

Abnormal hypothalamic-pituitary function in polyostotic fibrous dysplasia

Hypothalamic-pituitary dysfunction was found in two patients with polyostotic fibrous dysplasia and leontiasis ossea. Both patients probably had McCune--Albright syndrome with early sexual development, disfiguring craniofacial bone lesions, cutaneous hyperpigmentation and gigantism in childhood. Endocrinological studies revealed measurable plasma growth hormone throughout a 24-h sampling period with preservation of sleep augmented rises. The mean 24-h values were 329 and 7 ng/ml, respectively. Both their mean plasma prolactin concentrations, 385 and 45 ng/ml, and the 24-h secretory patterns of prolactin were abnormal. One patient had an elevated mean plasma cortisol concentration of 8.5 micrograms/dl but the 24-h pattern of cortisol secretion was normal. Basal plasma LH, FSH, TSH, T4 and T3 concentrations were normal but neither patient had a TSH response to TRH. Prolactin and growth hormone secretions were, however, increased after TRH. Oral glucose resulted in partial suppression of GH but an exaggerated insulin response in both patients. Post-mortem in one patient revealed a thick calvarium with bony encasement of the pituitary gland. The pituitary and hypothalamus appeared normal on gross, light microscopic and electronmicroscopic examination. These data strongly suggest the presence of hypothalamic-pituitary dysfunction in these two patients.

Hyperprolactinaemia in a patient with the McCune-Albright Syndrome

A patient is presented with the syndrome of polyostotic fibrous dysplasia and precocious puberty (McCune-Albright Syndrome). In adult life she developed hyperprolactinaemia with galactorrhoea and amenorrhoea; there was also evidence of excessive secretion of growth hormone.

McCune-Albright syndrome in a male child: a clinical and endocrinologic enigma

A 6 5/12-year-old boy with polyostotic fibrous dysplasia, café-au-lait pigmentation of the skin, and precocious pubertal development was studied for two years. Parathormone, calcium, phosphorus, testosterone, cortisol, and growth hormone levels were within normal limits. Urinary 17-ketosteroids, 17-ketogenic steroids, and estrogens were at the upper limits of normal. After GnRH stimulation, there was only a very slight increase in LH and no increase in FSH. There was no increase in TSH after TRH, and plasma levels of T4 and T3 were normal. The plasma prolactin level was within normal limits, and increased after TRH stimulation (with a second, delayed upsurge). Abnormal distribution of 131I in the thyroid was evident, without clearcut evidence of hyperfunctioning areas after TSH stimulation and T3 suppression tests followed by conventional scanning and gamma camera scintiphotography. Our findings do not support the claimed, single, hypothalamic origin of the disease that is presumed to result in overproduction of releasing hormones; they are more in keeping with a pleiotropic, scattered peripheral lesion, possibly of embryonal origin.

Cushing syndrome, sexual precocity, and polyostotic fibrous dysplasia (Albright syndrome) in infancy

The sexual precocity of polyostotic fibrous dysplasia is occasionally accompanied by other endocrine disorders, but in only two previous instances has Cushing syndrome been reported. The history of a 6-month-old girl is presented, in whom this syndrome was complicated by congenital Cushings syndrome. Although endocrinopathies of polyostotic fibrous dysplasia have usually been ascribed to a central (hypothalamic) origin, the findings in this patient suggest autonomous hyperfunction of the peripheral endocrine glands, with the Cushing syndrome caused by hyperplastic nodules in the adrenal glands and the precocity by luteinized follicular cysts of the ovary.

Growth hormone excess and sexual precocity in polyostotic fibrous dysplasia (McCune-Albright syndrome): evidence for abnormal hypothalamic function

A 5-5/12-year-old boy with gigantism and precocious puberty associated with the McCune-Albright syndrome is presented. Serum concentrations of growth hormone were extremely elevated (128-163 ng/ml) and were not suppressed by hyperglycemia or chlorpromazine. Serum LH (7.4 +/- 1.0 SD mIU/ml) and FSH (5.3 +/- 0.3 SD mIU/ml) concentrations were in the range observed in midpuberty. The secretion pattern of LH was episodic. The administration of estradiol suppressed the secretion of FSH and had an apparent positive feedback effect on release of LH. These findings are compatible with abnormal hypothalamic function as the mechanism for the endocrinopathies associated with the McCune-Albright syndrome.

Fibrous dysplasia

Three cases of monostotic fibrous dysplasia of the cranial bones are presented. Several theories of the etiology of this uncommon condition are put forward and the relationship between monostotic and polyostotic fibrous dysplasia, Albright's disease, and hyperparathyroidism is examined. The difficulty in diagnosis and the ways they may present to the ear, nose and throat surgeon are discussed. It is suggested that conservative surgery is the best mode of treatment for maxillary or temporal lesions. However, ethmoid lesions, particularly when the optic foramen or base of skull are eroded, may need a neuro-surgical approach. The use of radiotherapy in any case is deprecated.