1. DISORDERS OF THYROID HORMONE!
The disorders of the TH are among the most common of the endocrine disorders. The fall into 2 major categories: HYPER & HYPO thyroidism. A number of specific causes can give rise to the different disorders. Whatever the cause, the consequences of too little or too much TH are largely predictable, given that there is knowledge of the functions of the TH.

2. Thyroid hormones are NOT essential for life, but they do affect the QUALITY of life….
The main function of thyroid hormones in adults is to provide substrates for oxidative metabolism. Thyroid hormones are thermogenic & calorigenic in nature.

3. HYPERTHYROIDISM

4. Excess (increased) thyroid hormone secretion leads to Hyperthyroidism
Causes of Hyperthyroidism:
Primary Hyperthyroidism:
GRAVE’S DISEASE
THYROID ADENOMA
SUBACUTE THYROIDITIS
EXCESSIVE INTAKE OF IODINE
EXCESSIVE INTAKE OF EXOGENOUS THYROID HORMONE (THYROTOXICOSIS FACTITIA)
2. Secondary:
Secondary to increased TSH secretion (anterior pituitary adenoma)
Secondary to increased TRH secretion (hypothalamic tumor)

5. Diffuse enlargement of the gland
GRAVE’S DISEASE
(also called toxic goitre or thyrotoxicosis)
It is an autoimmune disorder in which abnormal thyroid stimulating immunoglobulins (TSI) attach to the TSH receptors on the thyroid gland. ↓
Diffuse enlargement of the gland
Stimulation of thyroid hormone secretion which suppress the TSH secretion from the Ant. Pituitary
↑ levels of TH + Goiter + Exophathalmos

6. Signs and symptoms of Hyperthyroidism
THYROID ADENOMA
(also called Nodular toxic disease or Plummer’s disease)
It is a localized adenoma or tumor that develops in the thyroid gland & secretes large quantities of thyroid hormone. ↓
↑ levels of TH
Signs and symptoms of Hyperthyroidism
Secretory function of the rest of the gland is almost totally inhibited as the thyroid hormone from the adenoma depresses the production of TSH from the anterior pituitary.

7. CLINICAL FEATURES Increased metabolism Weight loss Increased appetite
Involvement of CVS
Cardiac failure
Tachycardia
Atrial fibrillation
Raised pulse pressure
Murmurs
Involvement of Reproductive system
Impotence
Loss of libido
Oligomenorhea or polymenorrhea
Eye changes
Exophthalmos
Lid lag
Involvement of respiratory system & GIT
Breathlessness
Diarrheoa
Miscellaneous
Fine, silky hair
Pretibial myxedema
Thick brittle nails
Increased metabolism
Weight loss
Increased appetite
Heat intolerance
Warm moist skin
Sweating
Muscle weakness (thyrotoxic myopathy)
Involvement of CNS
Irritability/ behavior changes
Restlessness
Anger
Insomnia
Emotional instability
Psychosis
Fine Tremors
Brisk tendon reflexes
ALL THE PATIENTS OF HYPERTHYROIDISM CAN PROGRESS TO THYROID STORM IF LEFT UNTREATED

9. GRAVE’S DISEASE

10. EXPHTHALMOS: It is the protrusion of the eyeballs.
Usually seen only with Grave’s disease
CAUSE: Immunoglobulins are found in the blood that react with muscles of the eye ↓
Edema & swelling of retro-orbital tissue +
Degenerative changes in the extra-ocular muscles
Stare + Lid Lag
Failure of the eye to close completely esp. the upper lid fails to completely close
Dryness of the eye, irritation, infections, pain, double vision
In severe cases, protrusion of the eyeball stretches and damages the optic nerve leading to BLINDNESS

14. How will you diagnose HYPERTHYROIDISM?

15. Diagnosis of HYPERTHYROIDISM
↑ T3 & T4
↓ TSH
↓ TRH
However, both TRH & TSH will be raised if cause is excess hypothalamic or pituitary secretion: ↑ T3 & T4 & ↑ TRH & TSH
Anti-thyroid antibodies
TSI (Thyroid stimulating Immunoglobulins)
Scanning images show thyroid tumor if present

16. TREATMENT
3 options:
Anti-thyroid drugs
Surgery
Radioiodine

17. Size of thyroid gland & its blood supply decreased
ANTI-THYROID DRUGS
All the drugs that cause suppression of Thyroid hormone secretion are called Anti-thyroid drugs.
THIOCYANATE:
Prevent iodide trapping by competitively binding to sodium-iodide symporter instead of Iodide itself.
Percholate & nitrate ions also follow the same M.O.A.
It can lead to Goiter!! HOW?
PROPYLTHIOURACIL: e.g. methimazole, carbimazole
M.O.A: 1: partly blocks peroxidase enzyme
2 : partly blocks coupling
It also causes Goiter as it does not stop synthesis of TG.
IODINE:
If Increased Iodide conc. in the blood (more than 100 times) ↓
Most activities of the thyroid gland are decreased as IODIDE itself inhibits the enzymes needed for synthesis of TH
Size of thyroid gland & its blood supply decreased
So, Iodine usually given 2-3 weeks before surgery, to reduce the size of the gland decreasing the necessary amount of surgery & especially the amount of bleeding!!
With thiocyanates, decreased thyroid hormone secretion leads to increased TSH secretion. It stimulates the follicular cells & b/c thiocyanate is not preventing the TG production, synthesis of TG continues without check leading to increase in the size of the gland!

18. SITES OF ACTION OF ANTI-THYROID DRUGS

19. HYPOTHYROIDISM

20. Decreased secretion of Thyroid hormone is called Hypothyroidism.
PRIMARY HYPOTHYROIDISM
(due to primary failure of the Thyroid gland)
Hashimoto’s Thyroiditis
Endemic Colloid Goiter
Idiopathic Non-toxic Colloid Goiter
Tumors
Thyroiditis
Post-surgery
Post- Irradiation
2. SECONDARY HYPOTHYROIDISM
Secondary to decreased Hypothalamic secretion
Secondary to decreased anterior pituitary secretion or Decreased TSH secretion
3. DUE TO IODINE DEFICIENCY.

21. CAUSES OF HYPOTHYROIDISM (Primary causes)
1. HASHIMOTO’S THYROIDITIS:
It is an autoimmune disorder in which, like the Grave’s disease, there is production of abnormal antithyroid antibodies against the thyroid follicular cells and the TSH receptors. However, unlike the Grave’s disease where these antibodies were stimulatory, in Hashimoto’s disease the antibodies are inhibitory or block the Thyroid function and destroy the Thyroid gland.
This process develops very slowly.
Classical symptoms of Hypothyroidism are seen.
These patients may also develop other autoimmune disorders.

22. CAUSES OF HYPOTHYROIDISM (Primary causes)
2. ENDEMIC COLLOID GOITER caused by dietary Iodine deficiency in specific areas:
-In areas of Insufficient Iodine in the soil, the food does not contain even the minute quantities that are required .
-In the absence of iodized table salts, these populations develop very large goiters called Endemic goiters.
-M.O.A of production of a Goiter:
lack of Iodine ↓
Decreased secretion of T3 & T4
Increased secretion of TSH by the anterior pituitary
Stimulates the thyroid cells to secrete large amounts of TG into the follicular colloid
Gland grows larger & larger
Still no mature hormone, so TSH secretion continues
Stimulus by the TSH continues to stimulate the thyroid cells
Follicles enlarge tremendously & the gland may increase to times normal size

24. CAUSES OF HYPOTHYROIDISM (Primary causes)
3. IDIOPATHIC NON-TOXIC COLLOID GOITRE:
These patients do not have iodine deficiency
The thyroid hormone may be normal or (more frequently) depressed.
Usually, thyroiditis occurs which is inflammation of some or all of the thyroid follicles. The inflamed area then becomes replaced by the fibrous tissue and all secretory activity is lost: ↓
Decreased thyroid hormone secretion from the inflamed areas
Increased TSH secretion from the Anterior Pituitary
Enlargement of the non-inflamed parts of the thyroid gland
Therefore, nodular growth seen
- Also seen in populations eating Goitrogenic foods.e.g. turnips & cabbages

26. CLINICAL FEATURES DECREASED METABOLISM
Weight gain (not burning fuels at a normal rate)
Decreased appetite (decreased BMR)
Cold intolerance (lack of calorigenic effect)
Fatigue (lower energy production)
Cold peripheries (lower energy production)
Thin, dry skin, brittle nails and thinning hair: All due to effect on the protein metabolism.
INVOLVEMENT OF CNS
Mental sluggishness
Listlessness
Lethargy & fatigue
Somnolence
Psychosis
Depression
Poor memory
Slow reflexes
INVOLVEMENT OF CVS:
Cardiac failure
Bradycardia (due to reduction in rate and strength of cardiac contraction and a lowered cardiac output)
REPRODUCTIVE SYSTEM
Loss of libido
Mennorhagia or oligomenorrhea
GIT
Constipation
MISCELLANEOUS
FROG-LIKE HUSKY VOICE
Deafness
Loss of eyebrows

28. Protein+ hyaluronic acid+ chondroitin sulphate
MYXEDEMA
CAUSE: In patients with total lack of thyroid hormones, a condition known as Myxedema develops!!
Patients suffer from all the symptoms of Hypothyroidism and show following symptoms too:
There is characteristic accumulation of a water-retaining complex which forms the matrix in which other materials are deposited:
Protein+ hyaluronic acid+ chondroitin sulphate
SITE: interstitial spaces, particularly skin.
Because of its osmotic effect, this material causes the water to accumulate in these spaces, giving rise to the typical non –pitting edema seen in hypothyroid patients.
Atherosclerosis: leading to peripheral vascular disease, deafness & coronary artery disease & early death.
Myxedema coma
Myxedema depression

33. MYXEDEMA COMA
A clinical diagnosis at the end of a hypothryoid continuum. The patient is usually a case of undiagnosed Hypothyroidism OR was diagnosed but took no medication.
In such a patient the following symptoms are seen:
Bradycardia, Hypotension
Hypothermia
Hypoventilation
Stupor, Coma
Delayed deep tendon reflexes
Dry, puffy skin
Precipitating Factors:
Severe Illness
Infection
Cerebrovascular Accident
Seizure
GI Hemorrhage
Surgery
Sedative Drugs, Anesthetics

35. Hypothyroidism Lab studies
Decreased T4 and T3 levels.
Increased TSH (If the cause is Primary)
Presence of antithyroid antibodies (If the cause is Autoimmune)
Elevated cholesterol (due to poor secretion of cholesterol into the bile)

36. 1 daily oral tablet of thyroxine leads to complete cure!!
TREATMENT
There is only one treatment which is TH replacement except when the cause is Iodine Deficiency in which case IODINE should be given..
Thyroxine replacement:
1 daily oral tablet of thyroxine leads to complete cure!!
Iodine

37. CRETINISM
It is a condition in which the infant or the child has TH deficiency from birth.
CAUSE: extreme hypothyroidism during fetal life, infancy or childhood.
TYPES:
Congenital cretinism (absence of thyroid gland at birth).
Failure of the thyroid gland to produce the hormone due to a genetic defect. e.g: PENDRED Syndrome in which the protein PENDRIN is lacking.
Endemic cretinism (iodine lack in the diet)

38. CRETINISM CHARACTERISTICS:
A neonate without a thyroid gland may be of normal appearance & function b/c he was supplied by the mother in utero!
A few weeks after birth:
Movements become sluggish
Physical retardation (skeletal growth more retarded than soft tissue)
Mental retardation
Obese
Stocky
Short appearance
Large tongue sometimes to the extent that its huge size obstructs swallowing & breathing inducing guttural breathing that sometimes chokes the child.
Obese, stocky, large tongue b/c skeletal growth more retarded than the soft tissue growth which then seemed to be growing excessively!!

39. 6 MONTHS OLD BOY with CRETINISM & 4 MONTHS AFTER TREATMENT STARTED

40. CRETINISM
TREATMENT:
- Thyroid hormone replacement immediately within a few weeks as later no matter how much treatment given then irreversible, permanent mental retardation!

41. GOITRE
Large size of the thyroid gland OR thyroid gland enlargement is called Goitre.
Causes:
Physiological: puberty
pregnancy
Autoimmune disorder: Grave’s disease
Thyroiditis
Iodine deficiency goitre (endemic)
Goitrogens
Tumors
Multinodular goitre

42. GOITER CHARACTERISTICS:
It can cause dysphagia & difficulty in breathing, indicating oesophageal or tracheal compression!
The patients can show all the symptoms of Hypothyroidism Or Hperthyroidism depending on the cause of the goiter!