This document discusses hyperthyroidism, thyroid adenoma, and Graves' disease. It explains that these conditions are caused by TSH-like antibodies that bind to thyroid receptors and stimulate thyroid hormone production, overriding the normal negative feedback loop. It describes the signs and symptoms of overactive thyroid conditions as well as hypothyroidism and goiter. Treatment options for hyperthyroidism include surgery, antithyroid drugs, and radioactive iodine, while hypothyroidism is treated with thyroid hormone replacement therapy. Diagnostic tests include measuring thyroid hormone, TSH, and basal metabolic rate levels.

1. M.Prasad Naidu
MSc Medical Biochemistry,
Ph.D.Research Scholar

2.  1. Hyperthyroidism
 2. Thyroid Adenoma
 3. Grave’s disease

3.  Causes:
 Due to the presence of TSH like substances – proved
by RIA studies
 The conc of TSH was found to be 0/less in plasma of
Hyperthyroidism patients
 The TSH like substances are Abs which bind with
same membrane receptors of TSH
 These substances activate c-AMP system ↑T4
 These Abs act for long time (12hrs) (TSH-1hr)
 The ↑ of high T4 caused by Abs suppresses TSH
production
 Usually these Abs are developed b/cos autoimmunity

4.  Some times – localised tumor develops in
Thyroid tissue called Thyroidadenoma
 TA secretes large quantities of T4&T3
 It is not associated with autoimmunity
 As far as this adenoma remains active, the
other parts of Thyroid gland will not secrete
the hormone.
 This is b/cos the hormone from Adenoma ↓
depresses the production of TSH

5.  Autoimmune disease
 Normally TSH combines with surface
receptors of thyroid cells  syn of T4
 But in GD , the TSH autoAbs (B-TSAB)
produced by B-lymphocytes (Plasma cells)
activate the TSH-receptors & ↑ secretion of
T4

6.  Intolerance to heat ( due to ↑ BMR)
 ↑ sweating ( due to vasodialation)
 ↓ body wt ( Fat metabolism)
 ↑ motility of GIT  diarrhoea
 Muscular weakness  ↑protein catabolism
 Nervousness, extreme fatigue, inability to sleep, mild tremor
in the hands, psychoneurotic symptoms such as extreme
anxiety/worry (stimulation of CNS)
 Enlargement of Thyroid gland i.e, Toxic goiter
 Exophthalmos: Autoimmune
 some degree of protrusion of eye balls – if severe blindness
develops due to
 i)protrusion of eye ball stretches the optic nerve
 Ii) eye lids cannot be closed  dry  infection

7.  ↓ secretion of Thyroid hormones
 Autoimmune disease which causes
destruction of Gland
 In most patients it starts as the glandular
inflammation called – Thyroiditis
 Thyroiditis  fibrosis of the gland
 Hypothyroiditis Myxedema (adults)
Cretinism (Children)

8.  Due to hypothyroidism in adults
 Causes: occurs in severe conditions –
complete lack of thyroid hormones
 Signs & symptoms:
 Swelling of the face
 Bagginess under the eyes
 Non-pitting type of edema:- when pressed
it does not make pits and the edema is hard
(accumulation of Pro+cho.SO4 which form
hard tissue with ↑ accumulation of fluid)
 Atherosclerosis: ↑ cholesterol – blood ↑ bp

9.  Other general symptoms:
 Fatigue & muscular sluggishness
 Extreme somnolence ( 14-16 hrs/day)
 Menorrhagia & polymenorrhea
 ↓ Cordiovascular functions such as ↓heart rate, ↓
force of contraction of heart ↓ crodiac out put , ↓
blood volume
 ↑Body wt
 Constipation
 Mental sluggishness
 ↓ hair growth
 Scaliness of the skin
 Frog like husky voice

10.  Children
 Causes: congenital absence of thyroid gland
(genetic disorder or lack of I2 in diet)
 Features:
 The newborn baby may appear normal at birth (due
to supply of T4 from mother)
 But after few weeks – starts developing sluggish
movements croacking sound while crying 
mentally retarded
 Skeletal growth is more affected than soft tissues
 Tongue becomes so big – affects swallowing &
breathing
 Stunted growth

11. CRETINISM DWARFISM
Mental retardation Development of
Nervous system is
normal
Diff parts of the body
are disaapropriate
Proportionate
Reproduction system is
affected
normal

12.  Enlargement of thyroid gland
 Occurs both in hypothyroidism &
Hyperthyroidism
 Goiter in Hyperthyroidism  Toxic Goiter
 Due to tumor of the gland – Size ↑ - ↑
number of hormones secreting cells ↑
hormone level – Toxic Goiter
 Goiter in hypothyroidism –non toxic Goiter
 Only enlargement of gland – hormone
secretion is ↓

13.  Based on the cause, Non-toxic Goiter is of 2 types
 i) Endemic Colloid Goiter:-
 Due to lack of I2 – I2 intake <50µg/day
 Therefore no formation of hormones
 By feed back mechanism, hypothalamus and anterior pituitary
are stimulated
 This ↑ secretion of TRH and TSH  secretion of TGb
Follicles
 As there are no hormones to be cleaved, ↑ accumulation in
the follicles
 Therefore ↑ size of the gland
 In Swiss, Alps, Andes, Great region of US and in India –
Kashmir Valley Soil does not I2↓
 Therefore Food stuffs lack I2 – very common before the
introduction of iodized salts

14.  Enlargement of Thyroid gland occurs even
without I2 deficiency
 Exact cause not known
 These patients are first affected by
Thyroiditis which reduce synthesis of
Thyroid hormones
 Therefore secretion of TSH ↑
 ↑ Size of the gland
 In some persons the abnormal enzyme
system leads to Goiter(due to deficiency of
enzymes like peroxidase, iodinase and
deiodinase which are required synthesis of
T3&T4)

15.  Goitrogenic Substances: ( Goitrogens)
 Eg: Goitrin
 Contains antithyroid substances like
propylthiouracil
 Therefore TSH secretion ↑ enlargement of
Thyroid gland
 Goitrogens  in turnips, cabbage,
soyabeans
 The goitrogens become active only during
low I2 intake

16.  Treatment for Hyperthyroidism:-
 1. Surgical removal: Thyroidectomy
 2. Antithyroid substances:
Thiocyanate, thiourylenes, high conc of
inorganic iodides
 Treatment of hypothyroidism:
 Only treatment is administration of Thyroid
extract/ ingestion of pure thyroxine ( tablet)

17.  Drugs which supress the secretion of T3&T4
 1. Thiocyanate: the same active pump which
transports I- into Thyroid cells, transports
thiocyanate also
 So thiocyanate competitively inhibits I2
transport
 I2 transport is inhibited
 ↓ synthesis of Thyroxine

18.  Thiourea related substances
 Eg: Propylthiouracil and methimazole prevent the
formation of T4 from iodides and Tyr
 This is achieved by blocking peroxidase activity
and partly by blocking coupling of MIT & DIT
 During the use of these two antithyroid agents
even though the synthesis of Thyroid hormone is
inhibited , the formation of TGb is not stopped
 The deficiency of the hor ↑ TSH secretion ↑ Size
Thyroid gland with more secretion of TGb
 TGb accumation in gland  enlargement  non-
toxic G

19.  All phases of Thy.activity ↓
 ↓ release of Thyroxine
 ↓ Size
 ↓ blood supply
 Therefore iodides are frequently
administrated to hyperthyroid patients

20.  The most accurate diagnostic test is
Direct measurement of conc of Free thyroid
hormones in the plasma (T3&T4)
 Measurement of BMR:-
 In Hyperthyroidism, ↑ 30-60%
 In hypothyroidism, ↓ 20-40%
 The measurement of TRH and TSH:-
 In Hyperthyroidism total absence of TRH
& TSH (due to –ve feed back mechanism by
the ↑level of Thyroid hormones)