Thyroxine and Antithyroids

Hormones:

• The word harmones is derived from hormao which means to excite or
to rouse or set in motion.

• It is defined as a chemical substance which is formed in one organ
or released from one group of cell and carried in blood stream to another organ
or group of cell, to exert specific regulatory effect.

• The word hormones are secreted by endocrine gland.

• The word derived from Greek word endon=within and crinein = to set
a part.

• Like vitamins, hormones are effective in very low concentration.

• They do not have any cumulative action as they are destroyed and
excreted as soon as their function are over.

• Some hormones function quickly and are destroyed quickly e.g.
adrenaline.

• Some work slowly and destroyed slowly e.g –Thyroxine. 

Classifications of Hormones:

A. Chemically
hormones are classified as

Amino acid
derivatives:-e.g. Thyroxine, Liothyronine.

Polypeptides:-e.g.
Insulin,
Oxytocin, Vasopressin 

Proteins: e.g.
–growth hormones

Glycoprotein’s:-e.g.  FSH (follicle stimulating hormone, (LH)
Leutinising hormones.

Steroids:
e.g: Testosterone, Progesterone, And Oestradiol.

Miscellaneous:

a. Hormones
are classified according to source (origin).

1. Thyroids
hormones (hormones are secreted by thyroids gland) e.g. –
Thyroxine, Liothyronine, calcitonin

2. Pituitary
hormones:

• Hormones secreted by anterior pituitary: e.g. ACTH, TSH, FSH, LH,
GH.

• Hormones secreted by posterior pituitary: e.g Oxytocin,
Vasopressin 

3. Adrenal gland hormones:

• Secreted
by cortex: e.g. – Glucocorticoids like Cortisone, Hydrocortisone
Mineral corticoids like aldosterone

• Secreted
by medulla: adrenaline

4. Pancreatic
hormones:

• Secreted
by alpha cell of islets of langerhans: –e.g. glucagon

• Secreted
by beta cell of islets of langerhans: e.g. Insulin

5. Parathyroid hormones secreted by
parathyroid gland

6. Hormones
secreted by thymus gland – e.g Thymine

7. Hormones
secreted by hypothalamus:

• Releasing
factor for stimulation: e.g. Thyrotropin, (release TSH).
Adrenocorticotrophin (release ACTH), leutotrophin releasing hormones etc.

• Releasing
factor for inhibition of TSH, GH, FSH, etc.

Thyroxine

Structure
of Thyroxine:

Chemical name: 4-hydroxy
3, 5 –di-iodo phenyl) 3, 5 –di-iodo L-tyrosine

Physical properties
of Thyroxine:

• Its sodium salt is light yellow to buff coloured powder.

• It is odourless.

• It is tasteless.

• It is slightly soluble in water and alcohol.

• It is soluble in solution of alkali hydroxide and carbonates.

• It is levorotatory.

Chemical
properties of Thyroxine:

• When Thyroxine solution in alcohol is boiled with sodium nitrite
in presence of HCL it gives yellow colour which when made alkaline with dil
ammonia solutions gives red colour.

Stability
and storage of Thyroxine:

• It is hygroscopic but stable in dry air.

• It get discolored when exposure to light. Hence it is stored in
tightly closed light resistant containers.

Uses of
Thyroxine:

• To treat hypothyroidism.

• To suppress goiter.

• To treat cretinism

Pharmaceutical
dosage forms: Throxine
tablets

Brand names:
Eltroxin,
Roxil, Thyroglandin

Methimazole

Physical properties
of Methimazole:

• It is white or pale buff crystalline powder.

• It having faint characteristic odour.

• It is freely soluble in water alcohol and chloroform

Storage: it is
stored in well closed containers.

Uses of Methimazole:

• For long term control of hyperthyroidism such as grave disease

• For preparation of patients with hyperthyroidism prior to surgery.

• For temporary control of hyperthyroidism I ¹³¹
therapies.

Dosage
forms: Methimazole tablets

Brand names: Tapazole.

Propylthiouracil

Physical properties
of Propylthiouracil:

• It occurs as white or pale cream coloured crystal or crystalline
powder.

• It is odourless.

• It has bitter taste.

• It is very slightly soluble in water, alcohol, and chloroform.

• It is soluble in alkali hydroxide.

Chemical properties
of Propylthiouracil:

• When its saturated solution is boiled with a mixture of equal
volume of freshly prepared solution of sodium nitroprusside, hydroxyl ammonium
chloride and sodium carbonates it give greenish blue colour.

Storage: It is stored
in well closed containers.

Uses: As under
Methimazole.

Dosage
forms:  Polythiouracil
tablets

Brand names: Propacil