Endocrine Glands
Pritam S. Sahota, James A. Popp, Jerry F. Hardisty, Chirukandath Gopinath, Page R. Bouchard in Toxicologic Pathology, 2018
The endocrine system is one of the body’s major homeostatic control systems whose aim is to maintain normal function and development in the face of a constantly changing environment. Working in tandem with the nervous system, which is mainly responsible for rapid and immediate responses, the endocrine system tends to act in a slower and more sustained manner to regulate a diverse set of processes. Multiple endocrine glands also work in concert with one another to form complex feedback loops, which tightly regulate critical physiological processes. Like all homeostatic control systems, the capacity to maintain physiological parameters within normal bounds is finite, and when this capacity is exceeded by chemical or drug exposure, or environmental stressors, adverse consequences can ensue. Chemicals can cause endocrine abnormalities via different mechanisms, including direct alteration of hormone production, changes in the regulation of the hormonal axis, effects on hormonal transport, binding and signaling, as well as similar changes to counter-regulatory hormone systems. The objective of this chapter is to provide a broad overview of common spontaneous morphological changes in endocrine organs (pituitary gland, adrenal glands, thyroid gland, parathyroid gland, and the pancreatic islets), with examples of xenobiotic-induced changes, predominantly in rodents.
A Review of Classic Physiological Systems
Len Wisneski in The Scientific Basis of Integrative Health, 2017
The endocrine system is a system of internal structures that secrete hormones (mostly into the bloodstream) to regulate metabolism and perform myriad other bodily functions. The endocrine system is not as zippy as the nervous system. It turns an electrical signal into the elaboration of a single hormone or of several hormones, which then travel to various places in the body, communicating and directing physiological activity. The glands of the endocrine system include the pituitary, hypothalamus, thyroid, parathyroid, pancreas, adrenals, gonads (ovaries and testes), thymus, and the pineal gland (see Figure 1.7). In addition, there are various other organs with hormonal functions that are not technically considered to be endocrine glands, such as the previously discussed enteric system. In the first half of the twentieth century, scientists did not think of the brain as an endocrine organ. After nearly 15 years of work, two researchers, Roger Guillemin and Andrew V. Schally, identified the first hypothalamic secretion of hormones. In 1977, they both won the Nobel Prize for their efforts. Scientists continue to discover new hormones and neurotransmitters.
Endocrine System
David Sturgeon in Introduction to Anatomy and Physiology for Healthcare Students, 2018
In the previous chapter, we observed that the nervous system uses electrical signals to maintain a stable internal environment, as well as interpret sensory stimulation, generate voluntary movement and undertake mental activities involved in memory, intelligence and moral sense. The endocrine system, on the other hand, employs chemical messengers called hormones (from the Greek for ‘set in motion’) to influence and regulate cellular activity throughout the body. Although hormones are a much slower method of communication than nerve impulses (which can travel at a rate of up to 120 metres per second) they are capable of influencing many cells simultaneously and can exert a much longer duration of action. We produce more than 80 different hormones which govern and control every aspect of the human body to a greater or lesser extent. Although we will only discuss a few of these chemical messengers in this chapter, we should not underestimate how important they are to everyday health and well-being and it is no coincidence that we have already referred to many of them in the preceding chapters. It is also important to stress that the nervous and endocrine systems do not operate in isolation from one another, they work collaboratively in order to control and regulate cellular activity and to maintain homeostasis.
Thresholds of adversity and their applicability to endocrine disrupting chemicals
Published in Critical Reviews in Toxicology, 2020
Although in the embryo/fetus, the endocrine system is not fully functional and cannot ensure the homeostatic control of many vital processes of the organism, there are other homeostatic and repair mechanisms operating at the cellular level. In addition, there are hormonal homeostatic mechanisms operating in the maternal organism, which are able to counteract any initial perturbation induced by the chemical agent before delivery to the embyo/fetus. This again leads to the conclusion that a minimum level of interaction of the chemical agent with critical targets of the developing organism is required to elicit a toxicologically relevant effect. This critical level of interaction (threshold of adversity) might be lower in the developing organism than in the adult, and the nature of the effect might be different (severe, permanent damage in the fetus vs a less severe effect in the adult), but a threshold of adversity must exist (Piersma et al. 2011).
Mechanism of phthalate esters in the progression and development of breast cancer
Published in Drug and Chemical Toxicology, 2022
Mohd Mughees, Himanshu Chugh, Saima Wajid
Hormone induced breast cancer in females is not uncommon and the tendency of phthalates to work as endocrine disruptors put females at risk. Endocrine system is made up of multiple glandular organs that secrete hormones directly into bloodstream. Normal development of mammary gland involves endocrine signaling from hypothalamic-pituitary-gonadal axis (Macon and Fenton 2013). The endocrine disruptors are known to interfere in production, release, transport, binding, action and elimination of hormones which might further affect the development process in females (Macon and Fenton 2013). Diethylstilboestrol is a classic example of endocrine disruptor which has induced breast and cervical cancer in females (Brisken 2008). Endocrine disruptors might alter epithelial growth rate, stromal composition of gland, immune response, response to endogenous hormone, terminal end bud presence, inter-cell communication etc. (Macon and Fenton 2013). In addition, the disruption in development of breast at any of its development stage enhances the risk of breast cancer with other abnormalities (Macon and Fenton 2013).
ION cyclotron resonance: Geomagnetic strategy for living systems?
Published in Electromagnetic Biology and Medicine, 2019
Adding to this is the widely observed “opposites” nature for many ICR observations (Table 1) showing that many of the ICR effects reported can be reversed by simply tuning to a different ion. This effect was discovered by Smith (McLeod et al., 1987) who observed an enhancement in diatom motility under Ca2+ tuning but reduced motility for K+ tuning. Others subsequently (Lovely et al., 1993; Zhadin et al., 1999) extended these observations to rat behavior, finding that aggressiveness and memory were sharply altered by changing the ICR tuning frequency from Ca2+ to Mg2+. Although it is tempting to think of this as a sort of geomagnetic homeostasis, more detailed analysis suggests something else. The notion of homeostasis in biology essentially provides a number of autonomic pathways that serve to maintain the proper “setpoint” of the individual system. ICR stimulation is clearly different from homeostasis, in that in the latter case attempts are made to maintain the state of the system whereas ICR serves to alter the biological state. In one sense the action of the ICR field is similar to what the endocrine system does. The endocrine system directs a specific expression of the system to be either enhanced or reduced one way or the other, by means of pairs of antagonistic hormones (insulin/glucagen, estrogen/androgen, diuretic/vasopressin…).The ICR analogy is that instead of selected chemicals we find interactive resonance frequencies.
Related Knowledge Centers
- Parathyroid Gland
- Pineal Gland
- Circulatory System
- Thyroid
- Pituitary Gland
- Hormone
- Gland
- Hypothalamus
- Endocrine Gland
- Adrenal Gland