Focus on gonadotrophin signalling

Abstract

The crucial role of gonadotrophins in the regulation of reproductive functions has been known for a long time, and recent research has concentrated to a great extent on novel endocrine, paracrine and autocrine regulatory factors. The place of gonadotrophins in the treatment of infertility and hypogonadism is also well established, and their measurement is pivotal in the diagnostics of various reproductive disorders. Despite this established position and somewhat conservative image, novel information on the actions of gonadotrophins is constantly emerging. The developments of the last 10-15 years have brought the recombinant gonadotrophin preparations to clinical practice. Another development has been the discovery of mutations and polymorphisms in gonadotrophin subunit and receptor genes, which have unravelled totally new details in the physiology and pathophysiology of gonadotrophin synthesis, secretion and action (Themmen & Huhtaniemi 2000). Other novel findings of great importance have been the crystallization of gonadotrophin molecules; the latest development has been the crystallization of the extracellular FSH-receptor ligand-receptor complex (Fan & Hendrickson 2005), depicted on the cover of this issue of Reproduction. Finally, a number of transgenic mice with amplified gonadotrophin secretion and action, as well as knockout models for the gonadotrophin subunits and receptors have been produced. Besides providing the expected phenocopies of activating and inactivating mutations of the cognate human genes, these mouse models have presented us with novel and unexpected phenotypes caused by either defective or amplified gonadotrophin action.The four focus articles in this issue of Reproduction summarise the most important recent developments in our knowledge on the physiology and pathophysiology of gonadotrophin function, based on human mutations and relevant genetically modified mouse models. The first review (Themmen 2005) summarises the current knowledge about the mutations and polymorphisms detected in the human gonadotrophin subunit and receptor genes. Although the phenotypes of most of the possible activating and inactivating mutations of these genes are reasonably well known by now, gaps still exist in our knowledge. For instance, we do not understand why activating LH receptor mutations have no phenotype in women, and there is still only one report (Gromoll et al. 1996) on an activating FSH receptor mutation. The influence of several common polymorphisms of these genes on reproductive functions is currently being investigated, but we still do not understand the real importance of this genetic variability in human reproduction. Another unsolved question is the importance of the apparently wide extragonadal expression of gonadotrophin receptors, especially those of LH (Filicori et al. 2005). The second review (Costagliola et al. 2005) deals with some very intriguing spontaneous mutations in gonadotrophin receptors that affect the ligand-specificity of the hormone-receptor interaction. They also alude t...

Crossover of the Hypothalamic Pituitary–Adrenal/Interrenal, –Thyroid, and –Gonadal Axes in Testicular Development

“…In males, FSH is involved in the paracrine control and the structural and nutritional support of germ cell development of the Sertoli cells, while LH regulates androgen production in the Leydig cells (101, 102). The level of both gonadotropins, as well as related gene expression, can be altered by hyper- and hypothyroidic conditions in Mus musculus (8, 9, 68, 71).…”

Lampreys: Biology, Conservation and Control

“…The posterior part is somewhat thickened and is the terminating neurohemal structure for neurons whose cell bodies are in the preoptic region of the hypothalamus (Fig. The classical GpH family hormones each consist of two non-covalently bound subunits, α and β (Kawauchi et al 1989); within a species, the α subunit is the same among all the GpH family hormones, while the β subunits are different and convey hormone specificity (Kawauchi et al 1989;Swanson et al 1991;Huhtaniemi 2005). The lamprey adenohypophysis, in contrast to the neurohypophysis, is much better differentiated than in hagfishes (see Sower and Kawauchi 2011).…”

“…Two GTHs have been identified in all taxonomic groups of gnathostomes (Suzuki et al 1988;Kawauchi et al 1989;Quérat et al 2000Quérat et al , 2004Huhtaniemi 2005; Table 7.3). In placental mammals, there is an additional member of the glycoprotein hormone family called chorionic gonadotropin (CG).…”