ENDOCRINOLOGY: PANCREAS & GONADS

Pancreas

· Pancreas is the second-largest gland AFTER lIVER.

· It is a mixed type of gland, heterocrine in nature because it secretes both hormones and enzymes.
· Location: It is located in the curvature of the duodenum.
· Shape: Irregular leaf-like shape.

· Its weight is about 80 gm.

· Structure: Pancreas consists of 2 types of cells:

(i) Exocrine cells or acinar cells (98%) of the total volume of the pancreas): they are responsible for the secretion of pancreatic enzymes.

(ii) endocrine cells are the specialized glandular cells, found in scattered groups throughout the organs, known as the Islets of Langerhans or small islands (1-2 %).

· In 1869, Paul Langerhans demonstrated its endocrine functions for the first time.

· Total islets tissue consists of 1-3 per cent of the whole pancreatic tissue.
· Pancreatic islets has three types of cells: Alpha, Beta and Gamma Cells.

1. ɑ cells or alpha cells (20% islet cell mass): which secrete glucagons hormone and the cells are larger, granular and oxyphilic in nature.

2. β-cells or beta cells (60-40%) secrete the insulin hormone and are also granular but basophilic in nature.

3. γ-cells or D-cell or delta (ẟ) or gamma cells (15%) secrete the Somatostatin hormone or gastrin.

4. F- cell or PP Cells- it secretes the pancreatic polypeptide hormone.

1. INSULIN
· Insulin is synthesized by beta cells in the form of proinsulin.

· It has a molecular weight of 9000.

· Later, it changes into the active insulin.
· Function of Insulin:
· Insulin is the hypoglycemic anti-diabetic factor and proteinaceous in nature.

· So it shows the following functions:
· It lowers the blood glucose levels by stimulating the deposition of glycogen granules in the liver, glucose in the cells and skeletal muscles.

· It induces protein synthesis.
· It increases membrane permeability to certain nutrients.

· It helps in the formation of fat from glucose by preventing gluconeogenesis (conversion of fat and protein into glucose).
· Insulin secretion is principally controlled by blood glucose level.

· Eg, Hypoglycemia tends to decrease insulin secretion whereas hyperglycemia has the opposite effect.

2. GLUCAGON
· Glucagon is a hyperglycemic hormone produced by alpha cells of Islets of Langerhans.

· The hormone is a polypeptide consisting of 29 amino acids units in a single chain.
· Functions of Glucagons:
· Glucagon has antagonistic functions to that of insulin.

· Eg it elevates the blood sugar level by glycogenolysis, gluconeogenesis and lipolysis.

· So far no diseases are known to be caused by glucagons deficiency.

3. SOMATOSTATIN
· It inhibits the secretion of both hormones (insulin and glucagons) and the secretion of growth hormones.

4. PANCREATIC POLYPEPTIDE
· It is said to have some role in food absorption but the exact function is unclear.

DISORDER OF PANCREATIC HORMONE

· Deficiency of insulin or its complete lack causes a syndrome called diabetes mellitus which is characterized by the following symptoms:
· Hyperglycemia (high level of glucose in the blood),
· Polyuria (increase urine volume),

· Polydipsia (increased thirst),

· Polyphagia (increased appetite) (Or 3P),

· Ketonuria (presence of ketone bodies in urine),

· Glycosuria (presence of glucose in the urine),

· Acidosis (ph below 7),

· Hyponatraemia (low plasma sodium level)
· Rate of conversion of carbohydrates into fat is highly reduced but the formation of glucose from protein is increased to a great extent.

· Finally liver, the heart can damage and may need amputation of legs in severe cases.

Cells and Hormones released by them:

Cell type	Hormone	Function	Excess	Deficiency
A cell	Glucagon	Gluconeogenesis Glycogenolysis Lipolysis, Protein catabolism (Increases Blood glucose)	Hyperglycemia
B cell	Insulin	glucose uptake by cells. Lipogenesis Protein anabolism (Decreases Blood glucose)		Diabetes mellitus
C cell	Somatostatin	Secretion of insulin, GH, glycogen, TSH, ADH		Pseudohermaphroditism in males.
D cell	Pancreatic polypeptide

Types of Diabetes Mellitus:
· Two types of diabetes have been characterized:
1. Type I (Insulin-Dependent Diabetes Mellitus (IDDM) or juvenile diabetes mellitus:

· It results from the hereditary factor that causes the development of antibodies to the beta cells or due to atrophy of these cells.

· So there is a low secretion of insulin.
· It is found in children and young adults.

· It can be treated by diet control and insulin injection.

2. Type II or maturity-onset diabetes or Non- Insulin-Dependent Diabetes Mellitus (NIDDM)
· It occurs in older age and is caused by degeneration of beta-cell.

· Their insulin level is normal or elevated but tissue response to insulin is below low.

· Obese people are prone to this diabetes because of the large quantities of insulin is required for this person.
· It can be treated by weight reduction, diet control, and hypoglycemic therapy.

Secondary Diabetes
· It is characterized by complications of acute and chronic pancreatitis.
· It can be treated by some drugs such as thiazides, corticosteroids etc.

Gestational Diabetes
· It develops during pregnancy and disappears after delivery.
· It predisposes to large birth weight or stillbirth.

Gonads

1. Testes as an endocrine gland
· Interstitial cells or Leydig's cells act as the endocrine part of the testis because it secretes testosterone hormone which is responsible for descent of testes in embryonic life and development and maintenance of secondary sexual characters and spermatogenesis in adults.

2. Ovaries as an endocrine gland
· Ovaries secrete two types of hormones:
a. Estrogens
· It is secreted by Granulosa cells and Theca interna.
· Functions: It helps in the growth of female genitalia, regeneration of endometrium, development of the ductal system of breasts and protein anabolism.

b. Progesterone
· It is secreted by the Corpus luteum of the ovary.
· Functions: It maintains endometrium and pregnancy, plays a role in thermogenic and in the development of lobules of the breast.

· It also produces the secondary sexual characters of females.

Also, Read our Other Notes related to Endocrinology of Mammals:

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