Chronobiology in the endocrine system
Biological signaling occurs in a complex web with participation and interaction of the central nervous system, the autonomous nervous system, the endocrine glands, peripheral endocrine tissues including the intestinal tract and adipose tissue, and the immune system. All of these show an intricate time structure with rhythms and pulsatile variations in multiple frequencies. Circadian (about 24-hour) and circannual (about 1-year) rhythms are kept in step with the cyclic environmental surrounding by the timing and length of the daily light span. Rhythmicity of many endocrine variables is essential for their efficacy and, even in some instances, for the qualitative nature of their effects. Indeed, the continuous administration of certain hormones and their synthetic analogues may show substantially different effects than expected. In the design of drug-delivery systems and treatment schedules involving directly or indirectly the endocrine system, consideration of the human time organization is essential. A large amount of information on the endocrine time structure has accumulated, some of which is discussed in this review.
The Impact of Opioids on the Endocrine System
Opioids have been used for medicinal and analgesic purposes for centuries. However, their negative effects on the endocrine system, which have been known for some times, are barely discussed in modern medicine. Therefore, we conducted a systematic review of the impact of opioids on the endocrine system.
A review of the English language literature on preclinical and clinical studies of any type on the influence of opioids on the endocrine system was conducted. Preliminary recommendations for monitoring and managing these problems were provided.
Long-term opioid therapy for either addiction or chronic pain often induces hypogonadism owing to central suppression of hypothalamic secretion of gonadotropin-releasing hormone. Symptoms of opioid-induced hypogonadism include loss of libido, infertility, fatigue, depression, anxiety, loss of muscle strength and mass, osteoporosis, and compression fractures in both men and women; impotence in men; and menstrual irregularities and galactorrhea in women. In view of the increased use of opioids for chronic pain, it has become increasingly important to monitor patients taking opioids and manage endocrine complications. Therefore, patients on opioid therapy should be routinely screened for such symptoms and for laboratory abnormalities in sex hormones.
Opioid-induced hypogonadism seems to be a common complication of therapeutic or illicit opioid use. Patients on long-term opioid therapy should be prospectively monitored, and in cases of opioid-induced hypogonadism, we recommend nonopioid pain management, opioid rotation, or sex hormone supplementation after careful consideration of the risks and benefits.
The endocrine system and ageing
Complex changes occur within the endocrine system of ageing individuals. This article explores the changes that occur in the metabolism and production of various hormones and discusses the resulting clinical consequences. As individuals age there is a decline in the peripheral levels of oestrogen and testosterone, with an increase in luteinizing hormone, follicle-stimulating hormone and sex hormone-binding globulin. Additionally there is a decline in serum concentrations of growth hormone, insulin-like growth factor-I and dehydroepiandrosterone and its sulphate-bound form. Even though there are complex changes within the hypothalmo–pituitary–adrenal/thyroid axis, there is minimal change in adrenal and thyroid function with ageing. The clinical significance of these deficiencies with age are variable and include reduced protein synthesis, decrease in lean body mass and bone mass, increased fat mass, insulin resistance, higher cardiovascular disease risk, increase in vasomotor symptoms, fatigue, depression, anaemia, poor libido, erectile deficiency and a decline in immune function. For each endocrine system, studies have been carried out in an attempt to reverse the effects of ageing by altering the serum hormonal levels of older individuals. However, the real benefits of hormonal treatment in older individuals are still being evaluated. Copyright © 2007 Pathological Society of Great Britain and Ireland.
Assessing the Bioaccumulative Impact of Four Heavy Metals on the Endocrine System of Tilapia rendalli Fish Species in the Kafue River
Some heavy metals (HMs) are of biological importance in animal life while others are important trace elements for plant growth and in higher animals. Despite various uses, their biotoxic effects arise once accumulation levels in animal bodies go beyond maximum permissible limits. Heavy Metal contamination is an environmental problem worldwide. This study aimed at assessing the bioaccumulative impact of Cd, Cu, Ni and Pb on the endocrine system of Tilapia rendalli fish in Kafue River, Zambia. Water samples collected in replicate, were stored at 8°C in polypropylene bottles. Samples were filtered at room temperature for analysis. Blood, gills, liver and muscles were extracted per fish sample collected from upper, middle and lower site of the river; KUP, ITT and SH respectively. Gills, livers and muscles were cleaned, oven dried at 110°C, weighed and digested using 55% nitric acid and 70% perchloric acid (ANALAR) at about 200 – 250°C on a hot plate to a transparent solution after disappearance of initial brown fumes. Solutions were cooled and diluted using distilled water. The samples were assayed for the metals using FAAS. Blood samples were thawed at room temperature, centrifuged to collect supernatant serum. Serum was assayed for Estradiol (E2) and Testosterone (T) using ELISA method. Hormone levels varied significantly among fish samples. This difference was related to variations of HM levels in fish tissues from respective sites. Highest mean levels of T (13.58±2.8 ng/mL) and E2 (774.33±66.98 pg/mL) were measured in SH while lowest levels of T (5.78±0.69 ng/mL) and E2 (63.75±45.39 pg/mL) were measured in ITT. The study showed that low levels of Cd, Cu, and Ni in SH correlated significantly to high hormone levels, while high levels of Cu in livers and muscles; 496.73±184.96 mg/kg and 43.68±18.32 mg/kg respectively recorded in ITT, correlated negatively to low hormone levels in fish. A positive correlation between hormone levels and Pb concentrations in tissues was observed. Therefore, HM bioaccumulation may affect expression levels of sex hormones in fish as shown in this study. Since the levels of HM were high in internal organs than in muscle (flesh), fish of Kafue River may be safe for consumption, but may pose a health risk if consumed together with internal organs. 
Osteoporosis in Hemophilia
Aim: The aim of this paper is to review the pathophysiology, risk factors, prevention and treatment of osteoporosis in persons with hemophilia (PWH).
Study Design and Methodology: In a search of PubMed up to September 24, 2013 using as keywords “osteoporosis” and “hemophilia” the author found 61 references, of which only the 22 focused on the aim of this study were revised.
Results: Prevention of osteoporosis in PWH is crucial. Risk factors are lack of hematological prophylaxis and development of an inhibitor (antibody) against the deficient coagulation factor, lack of exercise due to chronic pain and loss of joint function (hemophilic arthropathy), low body mass index and abnormal liver function because of viral infection (HIV, HCV). It has not been demonstrated that hemophilia has any effect on osteoclast development and/or osteoblast loss. Hemophilia does not impair mineral Ca/P/K mobilizations and metabolisms. Hemophilia does not have any general effects on the endocrine system. Substitution treatment with clotting factors does not interfere with the treatment of osteoporosis. Conclusion: Continuous primary hematological prophylaxis and rehabilitation and exercise are paramount in PWH. PWH over the age of 50 should have routine screening for detection of osteoporosis. In PWH prevention should encourage good habits (such as a diet adequate in calcium and vitamin D) and discourage harmful habits (such as tobacco, alcohol and immobilization). Osteoporosis is multi-facial. Osteoporosis ought to be promptly treated regardless of the underlying cause.
 Haus, E., 2007. Chronobiology in the endocrine system. Advanced drug delivery reviews, 59(9-10), pp.985-1014.
 Katz, N. and Mazer, N.A., 2009. The impact of opioids on the endocrine system. The Clinical journal of pain, 25(2), pp.170-175.
 Chahal, H.S. and Drake, W.M., 2007. The endocrine system and ageing. The Journal of Pathology: A Journal of the Pathological Society of Great Britain and Ireland, 211(2), pp.173-180.
 Kaile, B. and Nyirenda, J., 2016. Assessing the bioaccumulative impact of four heavy metals on the endocrine system of Tilapia rendalli fish species in the Kafue River. Annual Research & Review in Biology, pp.1-23.
 Rodriguez-Merchan, E.C., 2014. Osteoporosis in hemophilia. International Blood Research & Reviews, pp.48-55.