Hormone secretion, initiation

Cholelithiasis can develop as a result of decreased gallbladder contractility, especially in the absence of enteral or oral intake. Lack of intestinal stimulation reduces secretion of cholecys-tokinin, a peptide hormone secreted in the duodenum that induces gallbladder contractility. The best prevention of cholelithiasis is early initiation of enteral or oral feeding, as stated earlier (to stimulate secretion of cholecystokinin, gallbladder contraction and emptying, and intestinal motility). 

Central to enhancing understanding of the initiation of ripening is elucidation of the connection between plant-hormone secretion and the... 

Oxytocin is a peptide hormone secreted by the posterior pituitary that elicits milk ejection in lactating women. It may contribute to the initiation of labor. Oxytocin is released during sexual orgasm. 

Angiotensin II is an octapeptide, which was initially described as a potent vasoconstrictor agent. However, its functions have since been expanded to include regulation of cell growth, inflammation, electrolyte and water balance, hormone secretion, sympathetic nervous system activity, differentiation, and apoptosis. The discovery that it is produced both systemically and locally was instrumental in establishing a pivotal role for the peptide in several disease states, including hypertension, coronary heart disease, myocarditis, congestive heart failure, atherosclerosis, and nephrosclerosis. 

Hyponatremia occurs in approximately a third of patients in the first week or two after SAH and is related to the severity of the initial presentation. It is not usually caused by inappropriate antidiuretic hormone secretion but by salt wasting, in which there is excessive loss of salt and water by the kidneys with a decrease in plasma volume. Below a plasma sodium of approximately 125mmol/l, correction is necessary by plasma volume expansion (Berendes et al. 1997). 

I Adverse Effects. Side effects (see Table 54—6) of carbamazepine may fluctuate daily, paralleling the rise and decline of serum concentrations. The side-effect profile also may follow a circadian rhythm. Neurosensory side effects (e.g., diplopia, blurred vision, nystagmus, ataxia, unsteadiness, dizziness, and headache) are the most common, occurring in 35% to 50% of patients. These side effects are more common during initiation of therapy and may dissipate with continued treatment. Patients have variable threshold concentrations for the occurrence of CNS side effects. If the carbamazepine serum concentration is kept below the individual threshold, the CNS side effects can be minimized. Dosage manipulation, including the use of the controlled- or sustained-release preparations, should be tried before the patient is considered to be intolerant of carbamazepine. Carbamazepine may induce a hyponatremic hyposmolar condition that is similar to the syndrome of inappropriate antidiuretic hormone secretion. The incidence may increase with age. Periodic determinations of serum sodium concentration are recommended, especially in the elderly." ... 

C. Calcitonin Calcitonin, a peptide hormone secreted by the thyroid gland, decreases bone resorption and serum calcium and phosphate (Figure 42-2). Bone formation is not impaired initially, but ultimately it is reduced. The hormone has been used in conditions in which an acute reduction of serum calcium is needed, eg, Paget s disease and hypercalcemia. While calcitonin is approved for treatment of osteoporosis, it is questionable whether long-term use prevents fractures. Although human calcitonin is available, salmon calcitonin is most often selected for clinical use because of its longer half-Ufe and greater potency. Calcitonin is administered by injection or as a nasal spray. 

On the other hand, excess iodine intake may also inhibit thyroid function, by either inhibition of iodide organification (Wolff-Charkoff effect) or inhibition of Tg proteolysis with reduction in hormone secretion, and may manifest itself either as a goiter, as hypothyroidism with/without goiter, or as hyperthyroidism (0.01-0.6% in populations on iodine prophylaxis), the outcome depending on the initial and current iodine status and current thyroid dysfunction (European Commission, 2002). The comparison of iodine intake and concentrations of serum Tg at various physiological or pathophysiological conditions is shown in Table 6.1. 

Lithium salts have been used as safe adjuncts In the Initial treatment of thyrotoxicosis (75). Lithium Is concentrated by the thyroid gland (76), with a thyrold-to-serum ratio of more than 2 1, suggesting active transport. Lithium Ion Inhibits adenylate cyclase, which forms cAMP. Formed In response to TSH, cAMP Is a stimulator of the processes Involved In thyroid hormone release from the gland. Inhibition of hormone secretion by lithium has proved to be a useful adjunct In treatment of hyperthyroidism (77). 

With the development of knowledge concerning the role of pantothenic acid in intermediary metabolism, the critical importance of this vitamin to adrenocortical function becomes more understandable. When the adrenal cortex is stimulated by stressful situations, its function is to respond rapidly by secreting steroid hormones which initiate and maintain a variety of physiological reactions. Its ability to synthesize these hormones may depend on its capacity to mobilize energy rapidly. Pantothenic acid, as part of coenzyme A, plays a critical role in the oxidative metabolism of both carbohydrate and fatty acids and may also be involved directly in lipid synthesis. Therefore, a deficiency in pantothenic acid can create a situation in which the ability of the adrenocortical cells to secrete steroid hormones is seriously impaired. 

Hyponatraemia and seizures Hyponatraemia associated with SSRIs has been reported in the literature, particularly in the elderly and those with a low BMI [46 ]. The mechanism is generally considered to be via development of the syndrome of inappropriate antidiuretic hormone secretion [47 ]. A further case of hyponatraemia occurring immediately after initiation of sertraline in an elderly patient was reported, with the development of generalised convulsions [48 ]. 

Glucagon-like peptide-1 (GLP-1) is a hormone secreted by the intestinal L cells. It is involved in glucose homeostasis, in improving insulin secretion and the pancreatic beta-cell fimetion. On the other hand, the ghrelin is a hormone that is synthesized in the human stomach, being involved in meal initiation. The biological fimetions of ghrelin are to... 

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