HORMONE AND HORMONE ANTAGONISTS
PREPARED BY MR. ABHIJIT DAS
THYROID HORMONES
INTRODUCTION
Thyroid hormones, primarily thyroxine (T4)
and triiodothyronine (T3), are essential for regulating metabolism. The
hypothalamus releases thyrotropin-releasing hormone (TRH), which stimulates the
pituitary gland to release thyroid-stimulating hormone (TSH). TSH then prompts
the thyroid gland to produce and release T3 and T4, which exert their metabolic
effects throughout the body.
SYNTHESIS AND STORAGE
Thyroid hormones (T3 and T4) are
synthesized in the thyroid gland from iodine and the amino acid tyrosine.
Iodine is actively transported into the thyroid follicular cells, where it's
combined with tyrosine to form T3 and T4. These hormones are then stored in the
thyroid follicles until they're released in response to signals from the
pituitary gland to regulate metabolism and other bodily functions.
CLASSIFICATION
1.
Thyroid Hormone
Replacements:
·
Examples:
·
Levothyroxine (Synthroid)
·
L-Thyroxine (Euthyrox)
2.
Thyroid Hormone Analogs:
·
Examples:
·
Liothyronine (Cytomel)
·
Dextrothyroxine
LEVOTHYROXINE:
PHARMACOLOGICAL ACTIONS
Metabolic Effects:
- Increases
metabolic rate.
- Enhances
the breakdown of carbohydrates, fats, and proteins.
- Promotes
energy production.
Cardiovascular System (CVS):
- Increases
heart rate and cardiac output.
- Enhances
cardiac contractility.
- Lowers
serum cholesterol levels.
Brain Function:
- Supports
normal brain development in infants.
- Improves
cognitive function in adults with hypothyroidism.
Temperature Regulation:
- Helps
maintain body temperature within the normal range.
- Prevents
sensitivity to cold in hypothyroid individuals.
Growth and Development:
- Essential
for proper growth and development in children.
- Promotes
bone growth and maturation of the skeleton.
THERAPEUTICAL USES
1. Cretinism
2. Hypothyroidism
3. Myxedema
4. Goiter
ANTI THYROID DRUGS
Anti-thyroid drugs are medications that
inhibit the production or release of thyroid hormones and are primarily used to
treat hyperthyroidism.
CLASSIFICATION
1.
Thionamides:
·
Examples: Methimazole (Tapazole),
Propylthiouracil (PTU)
2.
Iodine-Containing
Compounds:
·
Examples: Potassium
Iodide (SSKI), Radioactive Iodine (I-131)
THIONAMIDES
MOA
The mechanism of action of thionamides is
to inhibit the incorporation of iodine into tyrosine residues and the
subsequent coupling of these iodinated tyrosine residues, which are essential
steps in the synthesis of thyroid hormones (T3 and T4).
IODINE CONTAINING COMPOUNDS
MOA
Iodine-containing compounds, such as
potassium iodide and radioactive iodine (I-131), work by saturating the thyroid
gland with iodine. This high iodine level reduces the thyroid's ability to take
up and concentrate iodine, ultimately lowering the production and release of
thyroid hormones, helping to treat hyperthyroidism.
PARATHORMONE
Parathormone (PTH) is a hormone produced
by the parathyroid glands that plays a crucial role in bllod calcium
regulation. It stimulates osteoclasts to break down bone, releasing calcium
into the bloodstream. PTH also enhances the reabsorption of calcium in the
kidneys and promotes the release of calcitriol, the active form of vitamin D,
which further increases calcium absorption from the intestines. These actions
collectively help maintain calcium homeostasis in the body.
TERIPARATIDE
MOA
Teriparatide stimulates bone formation by
increasing osteoblast activity, promoting new bone growth, and improving bone
density. It acts as an anabolic agent in the treatment of severe osteoporosis.
ADVERSE EFFECTS OF TERIPARATIDE:
1.
Hypercalcemia
2.
Nausea
THERAPEUTIC USES OF TERIPARATIDE:
1.
Treatment of severe
osteoporosis.
2.
Prevention of fractures
in postmenopausal women at high risk of fractures.
CALCITONIN
Calcitonin is a hormone that lowers blood
calcium levels by inhibiting calcium release from bone and increasing calcium
excretion by the kidneys. It is primarily used in the management of
hypercalcemia and for the treatment of osteoporosis.
SALMON CALCITONIN
Salmon Calcitonin is derived from the
salmon fish and used to treat osteoporosis and hypercalcemia.
MOA
Salmon calcitonin works by inhibiting bone resorption (the breakdown of bone)
and reducing calcium levels in the blood by directly inhibiting osteoclast
activity, leading to decreased bone loss.
THERAPEUTICAL USES
1.
Treatment of
postmenopausal osteoporosis.
2.
Management of
hypercalcemia, especially in cases related to malignancies.
ESTROGEN
Estrogen is a female
sex hormone produced primarily in the ovaries,
but also in smaller amounts in the adrenal glands and
fat tissues. It plays a key role in regulating
the menstrual cycle, promoting the development of
secondary sexual characteristics in females, and supporting reproductive health.
The basic pharmacology of estrogen
involves its interaction with estrogen receptors in target tissues, which can
be classified into two main types: ERα and ERβ.
Estrogen receptor activation influences gene expression and cellular responses.
PATHOLOGICAL ROLE OF ESTROGEN
1.
Breast Cancer:
Prolonged exposure to high levels of estrogen can increase the risk of breast
cancer. Estrogen promotes cell proliferation, and when this occurs in breast
tissue, it can lead to the development of malignant tumors.
2.
Ovarian Cancer:
Prolonged exposure to estrogen may be associated with an increased risk of
ovarian cancer.
3.
Endometriosis:
Estrogen is thought to contribute to the growth of endometrial tissue outside
the uterus, leading to endometriosis, a painful condition.
4.
Polycystic Ovary Syndrome
(PCOS): PCOS is characterized by hormonal
imbalances, including elevated estrogen levels, which can lead to irregular
menstrual cycles, ovarian cysts, and other symptoms.
5.
Osteoporosis:
A decrease in estrogen levels during menopause can lead to bone loss,
increasing the risk of osteoporosis and fractures.
CLASSIFICATION
Estrogens can be classified into several categories based on their origin and
properties:
1.
Natural Estrogens:
·
Natural estrogens are
endogenous hormones produced by the ovaries in females. The primary natural
estrogen in the human body is estradiol (E2).
·
Estrone (E1) and
estriol (E3) are also natural estrogens produced
in smaller amounts.
2.
Synthetic Estrogens:
·
Synthetic estrogens are
artificially created compounds that mimic the actions of natural estrogens.
They are often used in medications and hormone replacement therapy.
·
Common synthetic
estrogens include ethinyl estradiol, mestranol etc.
3.
Selective Estrogen
Receptor Modulators (SERMs):
·
SERMs are a class of
drugs that interact with estrogen receptors, acting as estrogen agonists in
some tissues and estrogen antagonists in others.
·
Examples of SERMs include
tamoxifen (used in breast cancer treatment and
prevention), raloxifene (used in osteoporosis
treatment and prevention), and bazedoxifene (used
for menopausal symptom relief).
PHARMACOLOGICAL ACTIONS
1.
Reproductive Effects:
·
Estrogen promotes the
development and maintenance of female secondary sexual characteristics,
including breast development and the distribution of body fat.
·
It plays a central role
in the regulation of the menstrual cycle and is necessary for normal ovulation
and the preparation of the uterine lining for potential pregnancy.
2.
Bone Health:
·
Estrogen helps maintain
bone density by inhibiting bone resorption (breakdown) and stimulating bone
formation. It is essential for preventing osteoporosis.
3.
Cardiovascular Effects:
·
Estrogen has a favorable
impact on the cardiovascular system. It can improve lipid profiles by
increasing high-density lipoprotein (HDL or "good" cholesterol)
levels and decreasing low-density lipoprotein (LDL or "bad"
cholesterol) levels.
·
It may also have
vasodilatory effects, helping to relax blood vessels and improve blood flow.
4.
Cognitive and Mood
Effects:
·
Estrogen may have
neuroprotective effects and can influence cognitive function and mood. Some
research suggests that estrogen may help with memory and mood regulation,
particularly in the context of menopause.
5.
Hot Flash Relief:
Estrogen replacement therapy is effective in reducing hot flashes and other
vasomotor symptoms associated with menopause.
6.
Hormone Replacement
Therapy (HRT):
·
Estrogen is a key
component of HRT, which is prescribed to relieve menopausal symptoms and manage
certain health conditions associated with hormone deficiencies.
CLINICAL USES
1.
Hormone Replacement
Therapy (HRT): Estrogen is used to alleviate
menopausal symptoms, such as hot flashes, vaginal dryness, and mood
disturbances, in postmenopausal women.
2.
Osteoporosis Prevention
and Treatment: Estrogen can help maintain bone
density and reduce the risk of osteoporosis, particularly in postmenopausal
women.
3.
Contraception:
Estrogen is a component of combined oral contraceptives, helping to prevent
pregnancy by inhibiting ovulation and altering cervical mucus.
4.
Treatment of
Hypogonadism: Estrogen therapy may be used to
address hormone deficiencies in individuals with conditions like Turner
syndrome or primary ovarian insufficiency.
5.
Breast Cancer Prevention:
In some cases, estrogen receptor modulators like tamoxifen may be used to
reduce the risk of breast cancer in high-risk individuals.
PROGESTERON
Progesterone is a naturally occurring
hormone in the body. As a drug, it's used to regulate the menstrual cycle,
support pregnancy, and in hormone replacement therapy to manage menopausal
symptoms.
CLASSIFICATION
1.
Natural Progestin:
·
Example: Progesterone
2.
Synthetic Progestin:
·
Example:
Medroxyprogesterone acetate (Provera)
3.
Third-Generation
Progestin:
·
Example: Desogestrel
(found in some birth control pills like "Desogen" or
"Ortho-Cept")
PHARMACOLOGICAL ACTIONS
1.
Uterus: It makes the
uterine lining thinner, which can prevent pregnancy.
2.
Cervix: It thickens
cervical mucus, making it harder for sperm to reach the egg.
3.
Vagina: Progestin can
sometimes cause vaginal dryness or irritation.
4.
Mammary Gland: It can
stimulate breast tissue, leading to changes like tenderness or growth.
5.
Body Temperature:
Progestin may slightly increase body temperature.
CLINICAL USES
1.
Birth control: It's used
in birth control pills and hormonal methods to prevent pregnancy.
2.
Hormone replacement
therapy (HRT): Progestin is part of HRT to manage menopausal symptoms.
3.
Treating menstrual
disorders: It can help regulate irregular periods or reduce heavy bleeding.
4.
Support during pregnancy:
It's sometimes prescribed to prevent miscarriages or preterm labor.
5.
Treating certain cancers:
Progestin can be part of cancer treatment plans, such as for uterine cancer.