Physiology
Endocrine
Cortisol is secreted by which of the following:
Answer:
Cortisol is secreted from the zona fasciculata of the adrenal cortex.Cortisol
Physiology / Endocrine / Adrenal Function
Last Updated: 26th July 2024
Cortisol and its analogues have powerful effects on glucose metabolism and all collectively classified as glucocorticoids (although they do have some mineralocorticoid action). Cortisol is secreted from the zona fasciculata of the adrenal cortex.
Regulation of Cortisol Secretion in Health
Cortisol release is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is released in response to corticotropin-releasing hormone (CRH) from the hypothalamus. Cortisol has a negative feedback effect on the hypothalamus and the anterior pituitary gland, inhibiting release of CRH and ACTH respectively.
The effects of cortisol are mediated by intracellular receptors that translocate to the cell nucleus after binding the hormone.
Cortisol is released during the course of normal physiological activity in a pulsatile pattern. Cortisol release displays a circadian rhythm, with the highest levels in the early morning.
Regulation of Cortisol Secretion in Stress
The primary stimulus for the increased release of glucocorticoids is stress, which is the result of exposure to adverse situations.
Stress response:
The stress response is driven by the amygdala, part of the forebrain that stimulates:
- activity in the hypothalamic CRH neurons
- activity in the sympathetic nervous system
- activity in the parasympathetic nerves that cause acid secretion in the stomach
- the feeling of fear
The actions of the two parts of the adrenal gland are complementary in response to stress. Catecholamines are released from the adrenal medulla to produce a rapid increase in cardiac output and the mobilisation of metabolic fuels. Corticosteroids produce a slower, more sustained response.
Regulation of Cortisol Secretion. (Image Modified by FRCEM Success. Original by Campos-Rodríguez R, Godínez-Victoria M, Abarca-Rojano E, Pacheco-Yépez J, Reyna-Garfias H, Barbosa-Cabrera RE, Drago-Serrano ME [CC BY 3.0 , via Wikimedia Commons)
Effects of Cortisol
Cortisol acts to:
- raise plasma glucose by stimulating gluconeogenesis in the liver and inhibiting peripheral glucose uptake into storage tissues
- increase protein breakdown in skeletal muscle, skin and bone to release amino acids
- increase lipolysis from adipose tissues to release fatty acids
- and at higher levels...
- mimic the actions of aldosterone on the kidney to retain Na+ and water and lose K+ ions
- suppress the action of immune cells
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
