The neuro control of the ovarain cycle - a hypothesis.

Since more than 100 years, it is known that pituitary function depends upon the function of higher centers in the brain. It was already assumed at this time that pituitary extracts could influence the gonads and postulated that their use could have practical applications. In 1926, the 'gonadal principle' was discovered revealing the regulation of ovarian function by the pituitary. The two pituitary hormones were called 'Prolan A' and 'Prolan B' which are responsible for ovarian function especially secretion of the hormones: 'lutein' and 'foliculin'. If the names of Prolan A and B are changed to follicle-stimulating hormone (FSH) and luteinizing hormone (LH), and the names of foliculin and lutein to estrogen and progesterone, it becomes obvious that the pituitary-gonadal relationship, as we know it today, was first described in 1930. Then, the next step was the isolation, sequence and synthesis of gonadotropin releasing hormone (GnRH) responsible for the secretion of gonadotropins (Gn). It could be shown that GnRH pulse frequency has differential effects on Gn secretion: low-frequency pulses of GnRH stimulate preferentially FSH and high frequency LH secretion. The pulse frequency control depends from a subpopulation of kisspeptin neurons within the infundibular region of the hypothalamus with coexpression of neurokinin B and dynorphin A - KNDy neurons showing a negative feedback to estrogen. A second group of kisspeptide neurons in the rostral periventricular area of the third ventricle is devoid of neurokinin-B and dynorphin, mediates positive feedback from estrogen and so induces the midcycle LH-surge. Therefore, the variability in the frequency and amplitude of GnRH pulsatility is central to the differential regulation of LH and FSH and thus ovarian follicle development, the correct selection of a single dominant follicle for ovulation, the LH surge and the luteal phase.

How to help the aging male? Current approaches to hypogonadism in primary care.

Hypogonadism is a common condition which occurs more frequently in older men. It is characterized by low testosterone (T) and is associated with symptoms which are often nonspecific. A key symptom is low libido, but it can also be associated with erectile dysfunction, reduced muscle mass and strength, increased body fat, reduced bone mineral density and osteoporosis, reduced vitality, and depressed mood. Hypogonadism is linked with a variety of comorbid conditions including erectile dysfunction, metabolic syndrome, diabetes, obesity, and osteoporosis. However, the condition is often underdiagnosed. T supplementation in hypogonadism is associated with a range of benefits including improved sexual function, increased lean body mass and/or reduced fat mass, and improved bone mineral density. A variety of T supplementation formulations are available. Although there is no evidence of increased risk of initiating prostate cancer with T supplementation, it is contraindicated in men with prostate cancer. It is important that primary care physicians are aware of both the signs and symptoms of hypogonadism, the monitoring and testing that is required and the merits and advantages of the various T preparations to ensure optimal management of the condition with a treatment approach that best suits patients' needs.

An Aging World--demographics and challenges.

The world has seen enormous changes over the past century, including historically unprecedented declines in mortality rates and increases in population, followed by equally unprecedented declines in fertility rates. This century will see a new set of demographic challenges, including a mix of falling fertility rates alongside persisting worldwide population growth, and the subsequent aging of populations in both developing and developed countries. The 20th century was the century of population growth; the 21st century will go into the history books as the century of aging. A holistic approach to this new challenge of the 21st century will necessitate a quantum leap in multidisciplinary and internationally coordinated research efforts, supported by a new partnership between industry and governments, philanthropic and international organizations. This collaboration we hope will enrich us with a better understanding of healthy aging, permit us to help to improve quality of life, prevent the preventable, and postpone and decrease the pain and suffering of the inevitable.