The thyroid gland is one of the endocrine glands, located immediately below the larynx on either side of and anterior to the trachea.
Physiological Anatomy of Thyroid
The thyroid gland is composed of large number of closed follicles filled with a secretory substance called colloid and lined with cuboidal epitheliod cells that secrete into the interior of the follicles. The major constituent of colloid is the large glycoprotein known as thyroglobulin, which contains the thyroid hormone.
Normal Weight: about 25 grams.
Thyroid Hormones:
1. Thyroxine or Tetraiodothryronine or T4
2. Triiodothyronine or T3
3. Calcitonin: an important hormone for calcium metabolism
Formation and Secretion of T3 and T4
Iodine requirement: is about 1 mg per week of ingested iodine is required to form normal quantities of thyroxine. To prevent iodine deficiency common table salt is iodized with one part of sodium iodide to every 100,000 parts of sodium chloride.
Steps of T3 and T4 formation:
Iodine + Tyrosine* Monoiodotyrosine
Diiodotyrosine
Monoiodotyrosine + Diiodotyrosine Triidothyronine (T3)
Diiodotyrosine + Diiodotyrosine Tetraiodothyronine or Thyroxine (T4)
Regulation of Thyroid Hormone Secretion
The rate of thyroid hormone secretion is controlled by a specific feedback mechanism which operates through the hypothalamus and anterior pituitary gland. This system can be explained as follows:
1. Effects of Thyroid Stimulating Hormone (TSH) on Thyroid Secretion: TSH is secreted by the Anterior Pituitary. It increases the secretion of thyroxin and T3 by the thyroid gland.
2. Hypothalamic Regulation of TSH: Hypothalamus secretes a thyrotropin releasing hormone (TRH) which increases the secretion of TSH by anterior pituitary and correspondingly increases the activity of the thyroid gland. Hypothalamus can also inhibit the secretion of TSH by secreting a hormone somatostatin.
3. Feedback regulation of Thyroid secretion: Increased levels of thyroid hormone in the body fluids decreases the secretion of TSH by the anterior pituitary, which ultimately leads to decreased secretion of thyroid hormone from the thyroid gland.
HYPOTHYROIDISM
Definition: This is a clinical condition resulting from deficient thyroid hormone secretion.
Types:
1. Cretinism or Congenital hypothyroidism: Hypothyroidism dating from birth and resulting in developmental abnormalities in known as cretinism. It my occur due to thyroid agenesis, ectopic or hypoplastic thyroid tissue, inherited disorders or hormonogenesis, and transplacental passage of thyroid stimulating hormone receptor blocking antibodies (such cases resolve spontaneously within 2 months)
2. Myxoedema: It is characterized by accumulation of hydrophilic mucopolysaccharides in the ground substance of the skin and other tissues leading to thickening of the facial features and doughy indurations of the skin.
Causes:
I: Secondary to Pituitary / Hypothalamic disease
II: Primary thyroidal causes:
1. Inhibition of synthesis of thyroid hormone:
(i) Iodine deficiency
(ii) Antithyroid drugs
(iii) Inherited enzyme defects
2. Destruction of Gland:
(i) Surgical Removal
(ii) Irradiation (radioactive iodine, external)
(iii) Autoimmune Disease (Hashimoto’s thyroiditis)
(iv) After thyroiditis (acute and subacute)
(v) Replacement by cancer or other diseases.
3. Agenesis
4. Idiopathic atrophy (related to Hashimoto’s)
Presentation of Hypothyrodism
Rheumotology Aches and pains, arthritis
Gynaecology Menorrhagia
Ophthalmologist Puffy Eyes
ENT Deafness, Hoarse Voice
Neurology Polyneuritis, Cerebellar Features
Dermatology Dry Skin, Alopecia
Psychiatry Mental Changes, Psychosis
Cardiologist Ischemia, Cardiac Failure
Gastroenterology Constipation
Surgery Carpal-tunnel Syndrome, Goiter
Hematology Anemia
Casualty Coma
Nephrology Puffy Face, Oedema
Fortuitous presentation Screening or routine biochemical profile
The general physician may see any of the above presenting features, but should consider hypothyroidism in any patient whose mental or physical or general health has changed without explanation.
CLINICAL FEATURES
CRETINISM
IN INFANTS
1. Persistence of physiological jaundice
2. Hoarse cry
3. Motionless body
4. Noisy breathing
5. Constipation
6. Sleeps all day
7. Skin feels cold and dry
8. Pallor
9. Puffy face
10. Feeding problem
IN CHILDREN
1. Short stature
2. Course features
3. Widely set eyes
4. Broad flat nose
5. Protruding tongue
6. Sparse hairs
7. Cool dry skin
8. Thick neck
9. Protrubent abdomen with umbilical hernia 10. Delayed and defective dentition
IN OLDER CHILDREN
1. Mental retardation
2. Delayed puberty
3. Prolonged tendon reflex relaxation time
4. Bulky muscles
5. Short Stature
INVESTIGATIONS
1. Biochemical screening of newborns for congenital hypothyroidism
2. X-Ray examination reveals retarded bone growth , delayed union of the epiphysis and delayed dentition.
3. Serum T3 and T4 level: Reduced
4. Serum T4 level: Reduced
MYXOEDEMA
SYMPTOMS
1. Onset: Insidious
2. General Symptoms:
(i) Weight gain (ii) Intolerance of cold (iii) Lethargy (iv) Somnolence
3. Nervous :
(i) Poor memory (ii) Lack of concentration (iii) Paraesthesia of hands (iv) Depression
4. Ears: Deafness
5. Cardio Vascular: Pain on effort , Shortness of breath
6. Throat: Hoarseness of voice
7. G I System: Anorexia, Constipation
8. Muscular: Aches and Pains, , Stiffness of muscles ,Muscle cramps
9. Female: Menorrhagia and Polymenorrhoea, Infertility, Galactorrhoea
10. Male: Complete loss of libido
SIGNS
General :
Short stature
Pallor
Skin: dry and cool, myxoedema, occasionally vitiligo
Hair: dry , coarse and tend to fall out
Face: dull, expressionless face with periorbital puffiness
Tongue: Large
Goitre: Small, firm and diffuse (Hashimoto’s Thyroiditis)
Nodular or diffuse (iodine deficiency)
Larynx : Voice husky with a changed timber
Cardio Vascular:
Bradycardia
Cardiac enlargement
Evidence of pericardial effusion – rare
G I System: Adynamic ileus, producing megacolon or intestinal obstruction
Neuro Muscular: Carpal Tunnel Syndrome, soreness, tenderness and weakness of the muscle of the thumb caused by pressure on the median nerve at the point at which it goes through the carpal tunnel of the wrist
Delayed relaxation of tendon reflexes (Hung-up reflex)
Polyneuritis
Cerebellar Ataxia
Hypotonia of muscles
Respiratory: Obstructive sleep apnea
Psychiatric: Mental dwarfism
Slowness of thought and speech
Psychosis (myxoedema madness)
Females: Hyperprolactinaemia with galactorrhoea
INVESTIGATIONS
Serum Thyroid Hormone Measurement
1. Serum T4 level is reduced
2. Serum T3 usually remains normal except in severely ill patients, so measurement is not very helpful
Serum TSH Measurement
1. Raised level of TSH indicates Primary Thyroid failure
2. Raised TSH with normal T4 is termed as “Subclinical Hypothyroidism”
3. TSH within or below normal range with low Serum T4 indicates Secondary Hypothyrodism
Autoantibody Measurement: Antithyroid peroxidase and antithyroglobulin antibodies are often present in high titre in Hashimoto’s thyroiditis
Serum Protein bound iodine: Low
Radioactive Iodine uptake: Low
Blood Count: Anaemia --- Iron deficiency, normochromic, normocytic, macrocytic, pernicious
Serum Cholesterol: Raised
ECG: Show bradycardia and evidence of cardiac enlargement
Basal Metabolic Rate: Low
DIFFERENTIAL DIAGNOSIS :
1. Chronic Nephritis
2. Pituitary Myxoedema
3. Obesity
4. Coronary Insufficiency
5. Menstrual Disorder
6. Anemia
7. Unexplained heart failure
8. Hyperlipidaemia
9. Neurasthenia
10. Depression
11. Primary Psychosis
COMPLICATIONS :
1. Hypothermia and Myxoedema coma : In severely ill patients, especially in the elderly in cold weather
2. Hyperlipidaemia and ischemic heart disease associated with longstanding hypothyroidism
TREATMENT :
Replacement Therapy: Administration of thyroxin; triiodothyonine is used occasionally in myxoedema come to produce more rapid effect.
Follow-up and Management :
1. Serum TSH should be measured 8 weeks after starting the treatment to check whether the dose needs to be increased and should be measured annually in patients on established treatment to ensure continuing compliance
2. Treatment is for life, except in mild cases occurring within the first 6 months after radioiodine treatment, pregnancy or partial thyroidectomy and in patients who are hypothyroid secondary to sub acute or silent thyroiditis.
HOMOEOPATHIC TREATMENT
The treatment of Hypothyroidism should be strictly based on the totality of symptoms and constitution. The totality in these cases guides for the miasmatic consideration which in this case generally is Sycotic and the constitution is Hydro-genoid. A remedy base on totality may be able to cure this problem on a long term basis. Some important medicines for the purpose are as follows:
Calcarea Carb, Thuja, Nat. Sulph, Graphites, Ammon Carb, Thyrodinum, Iodium, Nux Mosc, Lycopodium, Pulsatilla etc.