An abnormally flattened circadian cortisol cycle has been linked with chronic fatigue syndrome, insomnia and burnout. In healthy individuals, cortisol rises rapidly after wakening, reaching a peak within 30–45 minutes. It is released when the body is dehydrated and has potent water-conserving effects on the kidney. One important target of glucocorticoids is the hypothalamus, which is a major controlling centre of the HPA axis. ACTH is transported by the blood to the adrenal cortex of the adrenal gland, where it rapidly stimulates the biosynthesis of corticosteroids such as cortisol from cholesterol. There, CRH and vasopressin act synergistically to stimulate the secretion of stored ACTH from corticotrope cells. The idea that there is a critical period in which testosterone exerts organizing effects is key to the organizational-activational hypothesis.12,13 Testosterone exposure must occur during this critical period for the brain to be masculinized. Extensive evidence relates sexually dimorphic aspects of physiology to brain masculinization by the testicular perinatal testosterone surges in males.7-10 Hypothalamic structure and function are modified by testosterone, leading to sex differences in reproductive behavior and physiology.10 We also discuss how the metabolic effect of testosterone is centrally mediated via the androgen receptor. We compare the organizational actions of testosterone, which program the hypothalamic control of metabolic homeostasis during development, and the activational actions of testosterone, which affect metabolic function after puberty. Testosterone deficiency predisposes men to metabolic dysfunction, with excess adiposity, insulin resistance, and type 2 diabetes, whereas androgen excess predisposes women to insulin resistance, adiposity, and type 2 diabetes. One of the most sexually dimorphic aspects of metabolic regulation is the bidirectional modulation of glucose and energy homeostasis by testosterone in males and females. The male reproductive system is not just about creating sperm, however. In humans, this process involves the intricate interplay of male and female reproductive systems—each a masterwork of evolutionary design. Perinatal androgen excess most likely involves central AR, as we observe alterations in the hypothalamic melanocortin system. There are several regions of the brain that regulate glucose and energy homeostasis and also express AR.39-42 Only the most likely regions for androgen action on metabolism will be discussed here. In control and hpg vasa deferentia, this stimulus produced contractions that peaked and then waned during the period of application (Fig. 5C and D). D–F, bar graphs showing the peak amplitude of contractions of control, hpg and hpgT vasa deferentia to phenylephrine, α,β-methylene ATP and 60 mm K+. The higher concentration of phenylephrine produced smaller amplitude contractions of the circular muscle in hpg vasa deferentia (Fig. 5A and D). In the presence of both DMI and rauwolscine, the further addition of prazosin (0.1 μm) almost abolished contractions of hpg vas deferentia (reduced by 98 ± 1%) whereas those of control vasa deferentia were reduced (by 68 ± 4%). B and C, bar graphs showing the relative change in contraction of control, hpg and hpgT vasa deferentia produced by prazosin (B) and suramin (C). However, it is not certain whether the increased mPFC activity actually temporally precedes the onset of tears, which is extremely difficult to determine, or that it rather reflects the awareness of the initiation of crying in the brain. In this study, only the activity of the medial prefrontal cortex (mPFC) was recorded in a very small sample of 8 individuals who cried in response to an emotional movie. This structure thus seems particularly involved in the motoric-vocal aspects of emotional expressions, specifically the coordination of the activity of the laryngeal, oral-facial, and principal and accessory muscles of respiration and inspiration . The neural circuits involved in the different components of emotional crying (i.e., muscular activity, vocalization, tear production, emotional experience) appear to primarily include structures that are part of the central autonomic network (CAN) . However, there was some differentiation in responses as well—around the peak onset, chills were accompanied by increased electrodermal activity, whereas tears were accompanied by decreased electrodermal activity, indicating a reduction in psychophysiological arousal for tears and increased arousal for chills. These results thus suggest increases in both sympathetic and parasympathetic activity just before the onset of crying. In the post crying period, the balance of sympathetic to parasympathetic activation returned to baseline levels.
