Marc Lombes

Glucocorticoids Inhibit Diastrophic Dysplasia Sulfate Transporter Activity in Otosclerosis by Interleukin-6

Hypothesis/Objective: Otosclerosis is a bone remodeling disorder localized to the otic capsule and associated with inflammation. In vitro, increased activity of the diastrophic dysplasia sulf/te transporter (DTDST), which is implicated in bone metabolism, has been reported. Because glucocorticoids modulate the bone turnover and inhibit inflammatory processes, we investigated the effect of dexamethasone (Dex) on interleukin‐6 and DTDST in otosclerosis.

Mild pituitary phenotype in 3- and 12-month-old Aip-deficient male mice.

Germline mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene predispose humans to pituitary adenomas, particularly of the somatotroph lineage. Mice with global heterozygous inactivation of Aip (Aip(+/-)) also develop pituitary adenomas but differ from AIP-mutated patients by the high penetrance of pituitary disease. The endocrine phenotype of these mice is unknown. The aim of this study was to determine the endocrine phenotype of Aip(+/-) mice by assessing the somatic growth, ultradian pattern of GH secretion and IGF1 concentrations of longitudinally followed male mice at 3 and 12u2009months of age. As the early stages of pituitary tumorigenesis are controversial, we also studied the pituitary histology and somatotroph cell proliferation in these mice. Aip(+/-) mice did not develop gigantism but exhibited a leaner phenotype than wild-type mice. Analysis of GH pulsatility by deconvolution in 12-month-old Aip(+/-) mice showed a mild increase in total GH secretion, a conserved GH pulsatility pattern, but a normal IGF1 concentration. No pituitary adenomas were detected up to 12u2009months of age. An increased ex vivo response to GHRH of pituitary explants from 3-month-old Aip(+/-) mice, together with areas of enlarged acini identified on reticulin staining in the pituitary of some Aip(+/-) mice, was suggestive of somatotroph hyperplasia. Global heterozygous Aip deficiency in mice is accompanied by subtle increase in GH secretion, which does not result in gigantism. The absence of pituitary adenomas in 12-month-old Aip(+/-) mice in our experimental conditions demonstrates the important phenotypic variability of this congenic mouse model.

Pharmacology of Hormone Replacement Therapy in Menopause

Menopause represents the final stage of the continuous process of reproductive aging in a woman’s life, marking the end of her fertility. According to the World Health Organization (WHO), the natural menopause is defined as the permanent cessation of menstruation resulting from the loss of ovarian follicular activity (WHO Report, 1996). Preceded by endocrine and menstrual cycle changes described as “menopausal transition”, natural menopause occurs at an average age of approximately 51 years, although a high inter-individual variability is supported by results from epidemiological studies. However, occurrence of menopause outside the estimated normal age interval (45-55 years) is associated with increased morbidity, either when a late or on the contrary, a premature cessation of menstruation appears. A late menopause implies a longer exposure to estrogens and a possible increased risk for breast (Colditz, 1993; Kelsey & Bernstein, 1996) and endometrial cancer (Dossus et al., 2010; McPherson et al., 1996) or for venous thromboembolism (Simon et al., 2006). On the other hand, women entering menopause earlier are facing a hypo-estrogenic state for a longer period compared to women undergoing normal menopause. That is the case for about 1% of women, which are confronted with the diagnosis of primary ovarian insufficiency (POI). POI is defined by the presence of amenorrhea associated with elevated follicle-stimulating hormone (FSH) levels in the menopausal range in women younger than 40 years (Bachelot et al., 2009). Women facing a premature cessation of the ovarian function were shown to be at increased risk for premature death, cardiovascular disease, neurologic disease, mood disorders, osteoporosis or psychosexual dysfunction (Shuster et al., 2010). As the main rationale for these disorders was linked to hormonal changes, maintaining a certain level of ovarian steroids for a given period of time arose as an essential condition for conserving life quality in women (Wilson, [1966]). Accentuated by the increasing life span, researches related to menopause and its treatment have provided scientific community with an increased body of data during the last decades. However, different aspects regarding the benefit/risk balance or the ideal doses and routes of administration of hormone replacement therapy (HRT) in menopausal women remain uncertain (Grodstein et al., 1997; Rossouw et al., 2002).