A quick review Sam Craik Endocrinology A quick review Sam Craik

What is endocrinology B. Paracrine B A The transmission of a hormone message from one cell... Transports via the blood stream. Arrives at a distant cell elsewhere in the body. Triggering a response from this cell. A. Autocrine C. Endocrine C

Hormone Types - Peptide Synthesised from one or more amino acid. Peptides often produced as inactive pro-hormones. Can be stored in vesicles for quick release. Act at target’s plasma membrane. Second messengers activated. Rapid response. Examples: Serotonin (amino acid derived) T3, T4 (dipeptide) Insulin (polypeptide)

Hormone Types - Lipid Derived from lipids: often cholesterol, sometimes fatty acids. Cholesterol converted to pregnalone. From here it is converted to steroid hormones. Slow fluctuations in steroid homone levels. Lipid soluble - Act on intracellular receptors. This affects gene expression, slow response. Examples: Testosterone, Oestrogen, Progesterone. Cortisol Prostaglandins (Fatty Acid)

Anterior Pituitary Hypothalamus Ant Pituitary Target Growth Hormone Releasing Hormone (GHRH) Growth Hormone Cell division + Differentiation Thyrotropin Releasing Hormone (TRH) Thyroid Secreting Hormone T3 + T4 (Thyroid) Corticotrophin Releasing Hormone (CRH) Adrenocorticotrophin Hormone (ACTH) Cortisol (Adrenal Cortex) Prolactin Lactation (Mammary) Gonadotrophin Releasing Hormone (GnRH) Follicle Stimulating Hormone (FSH) Gonads Luteinizing Hormone (LH)

Posterior Pituitary Oxytocin – Induction of childbirth, milk ejection. Vasopressin – Increased water absorption in kidney. Both are produced in the Hypothalamus and transported down a nerve axon in vesicles to the posterior pituitary where it is released into the blood. This is Neuroendocrine action. A D D. Neuroendocrine

Feedback Postive and negative feedback can occur where a hormone within a series acts back on the earlier hormones to activate or inhibit their release. Hypothalamus Ant Pituitary Ovary GnRH FSH Oestrogen Hypothalamus Ant Pituitary Ovary GnRH FSH Oestrogen +ve Feedback -ve Feedback

Growth Hormone Deficiency Excess Hypothalamus Short Stature Loss of growth stimulation (bone and muscle growth, fat brakdown) Hypothalamus Excess Gigantism in children, excessive long bone growth. Acromegaly in adults, epiphyseal fusion occurred already. Growth in soft tissues and flat bones. GHRH Ant Pituitary Growth Hormone Liver IGF-1

Thyroid Hormones Deficiency Hypothyroidism Congenital Control rate of cellular metabolism Deficiency Hypothyroidism Congenital Iodine Deficiency Hashimotos (AI) Tiredness Weight Gain Memory problems Depression Goitre Hypothalamus Excess Hyperthyroidism Graves Disease (AI) Restlessness Weight Loss Irritability Goitre TRH Ant Pituitary TSH Thyroid T3 + T4

Glucocorticoids Deficiency Addison’s Disease Hypothalamus Deficiency Addison’s Disease Destruction of Adrenal Cortex causes reduction in production of glucocorticoids (eg: Cortisol), mineralocorticoids and sex steroids. Often autoimmune Sometimes Tubercolosis Weight loss Anorexia Weakness CRH Ant Pituitary ACTH Adrenal Cortex Cortisol

Glucocorticoids Excess Cushing Syndrome Hypothalamus Excess Cushing Syndrome Can be at hypothalmic, pituitary or adrenal level. Cortisol has a negative feedback on ACTH. Can use ACTH levels to detect where problem is. High ACTH = Hypothalamus or Pituitary, excess ACTH produced. Low ACTH = Adrenal Cortex, excess Cortisol independent of ACTH, feeds back to inhibit. Thin limbs (fat/muscle breakdown) Central weight gain (storage of released fats/glucose) CRH Ant Pituitary ACTH Adrenal Cortex Cortisol