Proximate control of the development of sexual dimorphism is still hotly debated in reptiles. In some squamates, many male-typical exaggerated traits including body size were assumed to be controlled by masculinization by male gonadal androgens. We performed a manipulative experiment to test the importance of this mechanism in the development of pronounced sexual differences in body size and size of head casque in the chameleon Chamaeleo calyptratus. Castrated males attained male-typical body size highly deviating from the body size of control females. Ontogenetic allometries of casque size on head length revealed that sexes depart considerably in casque growth later in the ontogeny; however, castrated males still follow male-typical casque growth. Paradoxically, exogenous testosterone led in females to slight increase of casque size, which might reflect interference with the feminizing effects of female gonadal hormones. The results in males strongly suggest that masculinization by male gonadal androgens during growth is not required for the development of sexual dimorphism in body size and casque size in the chameleon. The ontogeny of sexually dimorphic body size and exaggerated traits in at least some squamates is likely controlled by other proximate mechanism, possibly by feminization by ovarian hormones.
- MeSH
- androgeny genetika metabolismus MeSH
- gonády metabolismus MeSH
- ještěři anatomie a histologie genetika růst a vývoj metabolismus MeSH
- kastrace MeSH
- lebka anatomie a histologie metabolismus MeSH
- pohlavní dimorfismus * MeSH
- testosteron genetika metabolismus MeSH
- velikost těla genetika MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- androgeny MeSH
- testosteron MeSH
OBJECTIVE: The first aim of our study was to define the hypogonadism manifested by low testosterone levels and incomplete male secondary sex characteristics in a 20-year-old male homozygous MC4R mutation carrier (G181D). The second aim of our study was to evaluate the effect of the anti-obesity drug sibutramine in this patient who failed to respond to an intensive lifestyle intervention and exhibited continuous weight gain. CASE REPORT: Anthropometric, biochemical, hormonal and psycho-behavioural parameters were investigated both at baseline and after a 1-year sibutramine treatment. To characterise the hypogonadism, sex steroid profile, concentrations of luteinizing hormone and follicle-stimulating hormone were determined. Standard tests with gonadotropin-releasing hormone, thyrotropin-releasing hormone and human chorionic gonadotropin were conducted. Brain magnetic resonance imaging was performed to exclude organic hypothalamic-pituitary lesions. Clinical examination and endocrine investigations revealed hypogonadotropic hypogonadism. Sibutramine induced body weight maintenance as well as improvement in body composition and obesity-related metabolic abnormalities. CONCLUSION: We described the first case of hypogonadotropic hypogonadism in a MC4R homozygous mutation carrier. The potential association between the hormonal disturbance and the hypothalamic derangement caused by the MC4R mutation should be considered. In addition, we demonstrated that sibutramine treatment had a favourable effect on body weight maintenance and obesity-related health risks.
- MeSH
- anorektika farmakologie terapeutické užití MeSH
- cyklobutany farmakologie terapeutické užití MeSH
- dospělí MeSH
- gonadotropiny krev genetika MeSH
- homozygot MeSH
- hypogonadismus komplikace farmakoterapie genetika MeSH
- lidé MeSH
- metabolické nemoci farmakoterapie etiologie MeSH
- mladý dospělý MeSH
- mutace * MeSH
- obezita komplikace farmakoterapie metabolismus MeSH
- pohlavní dimorfismus MeSH
- riziko MeSH
- složení těla účinky léků genetika MeSH
- tělesná hmotnost účinky léků MeSH
- testosteron krev genetika MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- kazuistiky MeSH
- práce podpořená grantem MeSH
- Názvy látek
- anorektika MeSH
- cyklobutany MeSH
- gonadotropiny MeSH
- sibutramine MeSH Prohlížeč
- testosteron MeSH
Testosterone (C19H28O2), the main testicular hormone, is 19-carbonic steroid substance with -OH group in position 17. Precursor for its synthesis is cholesterol, or possibly androstendione released by adrenal cortex. Testosterone is produced in smooth endoplasmatic reticulum of Leydig cells of testes. Apart from testes it is also produced in adrenal cortex, liver, kidneys, in fat and muscle tissue, even though in smaller extent--around 5% (Bidlingmaier, F. et al., 1986). Approximately 4-9 mg (13.9-31.2 nmol/l) of testosterone is daily produced in healthy men. Absolute majority, around 99% from overall plasmatic testosterone is bound to albumin, erythrocytes, but mainly to sex hormone binding globulin (SHBG) (Diver, M.J. et al., 2003). Only small proportion (1-2%) of testosterone circulates as free fraction (Ostatníková, D., 2003). Production and secretion of the main androgen in testes is regulated by well known and accepted axis of hypothalamus, hypophysis and testes. Testosterone and its metabolite dihydrotestosterone can influence the expression of genes, development of masculine type of habitus and behavior, acting via androgen receptor (AR) (Zitzmann, M. and Nieschlag, E., 2003). Testosterone can affect also via its metabolites, whose production is conditioned by enzymes. In peripheral tissues is testosterone converted via aromatase to estradiol and via 5alpha-reductase to dihydrotestosterone (Weber, K.S. et al., 1999).
- MeSH
- androgenní receptory genetika metabolismus MeSH
- lidé MeSH
- polymorfismus genetický MeSH
- testosteron * genetika metabolismus fyziologie MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- Publikační typ
- anglický abstrakt MeSH
- časopisecké články MeSH
- přehledy MeSH
- Názvy látek
- androgenní receptory MeSH
- testosteron * MeSH
