The Endocrinology of Extrapyramidal System Disorders

Hypothalamic dysfunction and neuroendocrine and metabolic alterations in Huntington's disease: clinical consequences and therapeutic implications

Huntington's disease (HD) is a hereditary neurodegenerative disorder characterized by cognitive, psychiatric, behavioural and motor disturbances. Although the course of HD is also frequently complicated by unintended weight loss, sleep disturbances and autonomic nervous system dysfunction, the aetiology of these signs and symptoms remains largely unknown. In recent years, many novel findings from both animal and human studies have emerged that indicate considerable hypothalamic, endocrine and metabolic alterations in HD. However, a comprehensive overview of these findings is lacking and their precise clinical significance is far from clear. Therefore, in this review we attempt to put these recent developments in the field into perspective by integrating them with previous findings in a comprehensible manner, and by discussing their clinical relevance, with a special focus on body weight, sleep and autonomic functions in HD, which will also allow for the identification of future lines of research in this area.

Orphan neurones and amine excess: the functional neuropathology of Parkinsonism and neuropsychiatric disease

The aetiology and treatment of Parkinsonism is currently conceptualised within a dopamine (DA) deficiency-repletion framework. Loss of striatal DA is thought to cause motor impairment of which tremor, bradykinaesia and rigidity are prominent features. Repletion of deficient DA should at least minimise parkinsonian signs and symptoms. In Section 2, based on extensive pre-clinical and clinical findings, the instability of this approach to Parkinsonism is scrutinised as the existing negative findings challenging the DA deficiency hypothesis are reviewed and reinterpreted. In Section 3 it is suggested that Parkinsonism is due to a DA excess far from the striatum in the area of the posterior lateral hypothalamus (PLH) and the substantia nigra (SN). This unique area, around the diencephalon/mesencephalon border (DCMCB), is packed with many ascending and descending fibres which undergo functional transformation during degeneration, collectively labelled 'orphan neurones'. These malformed cells remain functional resulting in pathological release of transmitter and perpetual neurotoxicity. Orphan neurone formation is commonly observed in the PLH of animals and in man exhibiting Parkinsonism. The mechanism by which orphan neurones impair motor function is analogous to that seen in the diseased human heart. From this perspective, to conceptualise orphan neurones at the DCMCB as 'Time bombs in the brain' is neither fanciful nor unrealistic [E.M. Stricker, M.J. Zigmond, Comments on effects of nigro-striatal dopamine lesions, Appetite 5 (1984) 266-267] as the DA excess phenomenon demands a different therapeutic approach for the management of Parkinsonism. In Section 4 the focus is on this novel concept of treatment strategies by concentrating on non-invasive, pharmacological and surgical modification of functional orphan neurones as they affect adjacent systems. The Orphan neurone/DA excess hypothesis permits a more comprehensive and defendable interpretation of the interrelationship between Parkinsonism and schizophrenia and other related disorders.

Dysautonomia in Parkinson's disease: relationship to motor disability

Disturbances of autonomic nervous system functions are common in patients with Parkinson's disease (PD) and may develop as a result of pathology in centers of autonomic regulation such as the hypothalamus, brainstem, and sympathetic ganglia. We examined the relationship between the degree of motor disability, as determined from the Hoehn and Yahr scale (1967), and the presence of pandysautonomia, as determined by the assessment of noninvasive cardiovascular reflexes, in 29 unmedicated PD patients (mean age: 72.0 years, SD = 8.9). In addition, we investigated the relationship of pandysautonomia to CT scan measures of cerebral atrophy and to the presence or absence of pineal calcification. Nine patients (31.0%) were found to have pandysautonomia with deficits in both sympathetic and parasympathetic cardiovascular functions. Pandysautonomia was statistically related only to the degree of motor disability (p < .01). These findings demonstrate a significant association between motor disability and objective impairment of central cardiovascular functions in PD.

Reduced luteinizing hormone secretion in women with Parkinson's disease

Plasma luteinizing hormone (LH) levels were significantly lower in 10 postmenopausal women with Parkinson's disease (PD) compared to age-matched controls. The remaining hypophyseal hormones and gonadal steroids were similar in PD patients and in controls, suggesting a selective alteration of hypothalamic dopaminergic mechanisms which regulate LH secretion.