The Endocrine System: Hormones and Their Functions

Posted on Apr 3, 2025 in Biology

Endocrine System

Pituitary Gland

1. Anterior Lobe (Adenohypophysis)

• Gonadotropin Hormone: Regulates the gonads.
• Thyrotropin Hormone: Regulates the thyroid.
• Somatotropin Hormone: Influences growth and carbohydrate metabolism. (Hypersecretion: Gigantism; Hyposecretion: Dwarfism)
• Adrenocorticotropin Hormone: Stimulates hormone production in the adrenal cortex.
• Prolactin Hormone: Various functions related to reproduction and lactation.

2. Pars Media (Intermediate Lobe)

• Melanocyte-Stimulating Hormone (MSH): Controls skin pigmentation.

3. Posterior Lobe (Neurohypophysis)

• Oxytocin: Stimulates uterine contractions during labor and milk ejection.
• Vasopressin/Antidiuretic Hormone (ADH): Constricts blood vessels, increasing blood pressure, and reduces urine production. (Hyposecretion: Diabetes Insipidus)

Endocrine Diseases

(Hyper: Too much; Hypo: Too little)

Hyperfunction: Increased activity of an organ or system.

Hypersecretion: Excessive hormone secretion.

• Gigantism: Hypersomatotropism (Childhood)
• Addison’s Disease: Hypoadrenalism (Cortisol deficiency)
• Cushing’s Syndrome: Hypercortisolism
• Acromegaly: Hypersomatotropism (Adulthood)
• Myxedema: Hypothyroidism (Adults)
• Graves’ Disease/Basedow’s Disease: Hyperthyroidism with possible exophthalmos (protruding eyes)
• Dwarfism: Hyposomatotropism (Childhood)
• Hypogonadism: Hyposecretion of testosterone (men) or estrogen (women)
• Diabetes Mellitus: Type I – Pancreatic hypofunction; Type II – Pancreatic dysfunction
• Cretinism: Hypothyroidism (Childhood)
• Infertility: Hyposecretion of gonadotropins (FSH, LH)
• Polycystic Ovary Syndrome (PCOS): LH hyposecretion (women)
• Hirsutism (Virilism): Hyperandrogenism (women)
• Diabetes Insipidus: ADH hyposecretion
• Edema: ADH hypersecretion (fluid retention)

Glands

Endocrine Glands

Release hormones directly into the bloodstream to act on distant target organs.

• Pituitary Gland
• Adrenal Glands
• Thyroid Gland

Thyroid hormone influences:

• Cell Differentiation: Hyperthyroidism (accelerated); Hypothyroidism (limited, dwarfism)
• Excitability: Hyperthyroidism (increased); Hypothyroidism (decreased, symptoms of cognitive impairment)
• Metabolism: Hyperthyroidism (increased, weight loss); Hypothyroidism (decreased, obesity)

Amphicrine (Mixed) Glands

Act as both endocrine and exocrine glands.

• Pancreas: Produces pancreatic juice (exocrine) and hormones like insulin and glucagon (endocrine)
• Gonads: Produce gametes (exocrine) and sex hormones like testosterone, estrogen, and progesterone (endocrine)

Exocrine Glands

Release secretions through ducts onto internal or external body surfaces.

• Sweat Glands
• Salivary Glands
• Lacrimal Glands (Tears)
• Mammary Glands (Milk)
• Mucous Glands
• Gastric Glands

Characteristics of Endocrine Control

1. Control occurs through hormones produced in endocrine glands.
2. Effects are long-term.
3. Act at a distance on target organs, which may be other endocrine glands.
4. Control and regulate body systems along with the nervous system.
5. Hormone deficiencies (hypo) or excesses (hyper) can cause endocrine diseases, which can sometimes be treated by hormone replacement or suppression.

Hormone Characteristics

1. Hormones are internal secretions.
2. They are primarily protein-based.
3. They act in minute quantities.
4. They are transported by the blood.
5. They have specific target organs and can accelerate or decelerate biological processes.
6. They maintain physiological balance, largely controlled by the pituitary gland.

Diabetes Insipidus vs. Diabetes Mellitus