Endocrinology 1999–2000

Overview

Long-lasting problem on the differentiation of adenohypophyseal cell, which prepares them for their specific tasks(somatotropic, lactotropic ect.), becomes elucidated after recognition of the differentiational effect of transcriptionfactor Pit-1. Expression of that factor in somatotrops results in STH secretion, contrary to lactotrops producingprolactin. Subclinical hypothyreosis (increased TSH with normal T3 and T4) endangers vessel not because ofhypercholesterolemia, but because of changes in the dynamics of the blood flow. The idea of cardiotropic effect ofthyroidal hormones is supported by the finding that administration of trijodthyronine to children after the surgicalcorrection of heart malformations (cardiopulmonary bypass) improves myocardial function -⁠ it elevates cardiacoutput and decreases requirements on the intensive care. Receptors for hormones in tissues are flexible, they can be„heterooligomers” for dopamine and somatostatin. Mutations of mineralocorticoid receptor may cause hypertensionin pregnancy and progesterone receptors have several isoforms. Receptors can be also activated by short expositionto a hormone. Glucocorticoids have probably also membrane receptors. Diabetes mellitus „type I” needn’t to beimmunogenic and DM type II not only results from down-regulation of receptors and subsequent insulin resistance, butit can be also caused by defects in insulin secretion. Insulin has receptors in the brain and participates in the appetiteregulation. The attempt to use „desensibilisation” by peroraly administered insulin in patients with immunogenic DMhad no effect. Stress affects memory mechanisms, heavy emotional stress during gravidity can bring congenitalmalformations. The decrease of mental functions in aged women depends on the level of free estradiol (the fraction,which is not bound to plasma proteins). Activation of dopaminergic neurons can be achieved by neurotropic growthfactors. Nesiritide is a recombinant brain natriuretic hormone successfully tested in heart failure. The role of leptin inthe appetite regulation in man is still not clear, other signalling molecules may have also an effect, e.g., ghrelin, whichprimarily stimulates STH secretion and brings about weight gain. Sildenafil influences nitrergic neurons elsewhere thanin penis, for example it has positive effects in patients with oesophageal achalasia.

Key words:
adenohypophysa, transcription factor Pit-1, thyroxine effects, receptor flexibility, diabetes mellitus,mental functins, nesiritide, leptin, nitrergic regulations.