Hypothalamic‐pituitary‐gonadal Relationships in Man From Birth to Puberty

Abstract

Gonadal function depends upon activities at various levels. Thus there is: (a) a central level (extra-hypothalamic, hypothalamic, and anterior pituitary); (b) an intermediate level (gonadal and plasma), and (c) a peripheral level consisting of the target organs to which the hormonal message is directed. These determine both the expression of gonadal function (physical, physiological, or psychological) and the feedback regulation of the secretion of gonadotrophins.(a) Central level (i) Extra-hypothalamic centres. The production of LH releasing hormone (LHRH) is affected in the rat, and probably in primates as well, by extra-hypothalamic stimuli coming, in particular, from the amygdala and the hippocampus. Adrenergic regulation exists at this level, noradrenaline having a stimulatory and dopamine an inhibitory effect (Bliss et al., 1972).(ii) Hypothalamic centres. These are localized in particular in the pre-optic area. Immunochemical techniques have demonstrated that LHRH is secreted by neurones of the arcuate nucleus, and released into the capillary plexus proximal to the hypophyseal portal system at the level of the median eminence, thereby reaching the anterior pituitary (Barry & Dubois, 1974;Setalo et al., 1975).(iii) Gonadotrophin secreting cells of the anterior pituitary. These synthesize and secrete the gonadotrophins, LH and FSH, under the influence of LHRH (Schally et al., 1972). The pituitary gonadotrophins stimulate the synthesis and the secretion of the gonadal

High normal testosterone levels in infants with non-mosaic Klinefelter’s syndrome

“…This could be due to differences in hormone levels according to different assay platforms (23). Nevertheless, the reported levels of T in the control infants in the two KS studies were much higher (4-20 nmol/l (5th-95th percentiles); (14, 15)) than reported by any other study (2,3,5,(24)(25)(26)(27)(28), including this study.…”

Transient Increase in Postnatal Testicular Activity Is Not Revealed by Longitudinal Measurements of Salivary Testosterone

“…The latter levels decrease during the first postnatal week, but a prominent secondary peak appears before 3 months of age (1)(2)(3)(4)(5)(6). The low prepubertal levels of serum T are gradually reached toward the age of 12 months (1-6).…”

“…The testis tissue is clearly under increased gonadotropin support during months 1-3 of age, as demonstrated by measurements of circulating luteinizing hormone and follicle-stimulating hormone (2,4,6). The gonadotropin peak could be a result of decreased negative feedback from the testis, as reflected by the decreased bioactive fraction of circulating T. Experiments in rhesus monkeys show that the testicular negative feedback on gonadotropin secretion is functional in utero (1 3) and immediately after birth (14).…”

“…This has been documented by elevated levels of gonadotropins and T in single serum samples from individual boys (1)(2)(3)(4)(5)(6). However, owing to the cross-sectional nature of the previous studies, the timing and duration of testicular activity in individual boys is unknown.…”

Living or dying in three quarter time: Neonatal orchestration of hippocampal cell death pathways by androgens and excitatory GABA

“…During the 2nd half of fetal life, negative feedback becomes gradually established and this appears earlier in male fetuses than in females. During the perinatal phase, there is a further increase in circulating testosterone over the 1st 6 months of life (Forest et al, 1976). Circulating androgens, both testosterone and its primary metabolite, DHT, are synthesized and released from the testes during the perinatal period (Sokka and Huhtaniemi, 1995).…”