Endoc- THYROID- HYPETHYROID

Question 1

_____________is a hypermetabolic state caused by elevated circulating levels of free T3 and T4. Because it is caused most commonly by hyperfunction of the thyroid gland, it is often referred to as hyperthyroidism.

Answer 1

Thyrotoxicosis

Question 2

However, in certain conditions the oversupply is related to either_________________- or to an_________________________ ( Table 24-3 ).

Thus, strictly speaking, hyperthyroidism is only one (albeit the most common) cause of thyrotoxicosis.

Answer 2

• ** excessive release of preformed thyroid hormone (e.g., in thyroiditis)**
• ** extra-thyroidal source, rather than hyperfunction of the gland**

Question 3

The terms primary and secondary hyperthyroidism are sometimes used to designate hyperthyroidism arising from an __________________ and _________________.

With this caveat, we will follow the common practice of using the terms thyrotoxicosis and hyperthyroidism interchangeably.

Answer 3

• intrinsic thyroid abnormality
• ** and that arising from processes outside of the thyroid, such as a TSH-secreting pituitary tumor.**

Question 4

The three most common causes of thyrotoxicosis are also associated with hyperfunction of the gland and include the following:

Answer 4

• Diffuse hyperplasia of the thyroid associated with Graves disease (accounts for 85% ofcases)
• • Hyperfunctional multinodular goiter
• • Hyperfunctional adenoma of the thyroid

Question 5

TABLE 24-3 – Disorders Associated with Thyrotoxicosis
ASSOCIATED WITH HYPERTHYROIDISM

Answer 5

• Primary
• Secondary
• NOT ASSOCIATED WITH HYPERTHYROIDISM

Question 6

TABLE 24-3 – Disorders Associated with Thyrotoxicosis
ASSOCIATED WITH HYPERTHYROIDISM

Primary

Answer 6

• Diffuse toxic hyperplasia (Graves disease)
• Hyperfunctioning (“toxic”) multinodular goiter
• Hyperfunctioning (“toxic”) adenoma
• Iodine-induced hyperthyroidism
• Neonatal thyrotoxicosis associated with maternal Graves
• disease

Question 7

TABLE 24-3 – Disorders Associated with Thyrotoxicosis
ASSOCIATED WITH HYPERTHYROIDISM

Secondary

Answer 7

TSH-secreting pituitary adenoma (rare) [*]

Question 8

NOT ASSOCIATED WITH HYPERTHYROIDISM

Answer 8

• Granulomatous (de Quervain) thyroiditis (painful)
• Subacute lymphocytic thyroiditis (painless)
• Struma ovarii (ovarian teratoma with ectopic thyroid
• ) Factitious thyrotoxicosis (exogenous thyroxine intake)

Question 9

What is the clinical course of HYPERTHYROIDISM?

Answer 9

Clinical Course.
The clinical manifestations of hyperthyroidism are protean and include changes referable to the
hypermetabolic state induced by excess thyroid hormone and to overactivity of the sympathetic
nervous system (i.e., an increase in the β-adrenergic “tone”).

Question 10

Excessive levels of thyroid hormone result in an:

Answer 10

• increase in the basal metabolic rate.
• The skin of thyrotoxic patients tends to be soft, warm, and flushed because of increased blood flow and
• peripheral vasodilation to increase heat loss.
• Heat intolerance is common.
• Sweating is increased because of higher levels of calorigenesis.
• Increased basal metabolic rate also results in characteristic weight loss despite increased appetite.

Question 11

______________ are among the earliest and most consistent features of hyperthyroidism.

Answer 11

Cardiac manifestations

Question 12

What is the reason behind the cardiac manifestation in Hyperthyroidism?

Answer 12

Individuals with hyperthyroidism can have an increase in cardiac output, *due to both increased cardiac contractility and* increased peripheral oxygen requirements.

Tachycardia, palpitations, and cardiomegaly are common. Arrhythmias, particularly atrial fibrillation, occur frequently and are more common in older patients.

Congestive heart failure may develop, particularly in elderly patients with preexisting cardiac disease.

Myocardial changes, such as foci of lymphocytic and eosinophilic infiltration, mild fibrosis in the interstitium, fatty changes in myofibers, and an increase in size and number of mitochondria, have been described.

Question 13

Some individuals with thyrotoxicosis develop reversible left ventricular dysfunction and “low-output” heart failure, socalled ___________________.

Answer 13

thyrotoxic or hyperthyroid cardiomyopathy

Question 14

In the neuromuscular system, overactivity of the sympathetic nervous system produces____________________________

Proximal muscle
weakness and decreased muscle mass are common (thyroid myopathy).

Answer 14

• tremor,
• hyperactivity,
• emotional lability,
• anxiety
• , inability to concentrate,
• and insomnia.

Question 15

Ocular changes often call attention to hyperthyroidism.

A wide, staring gaze and lid lag are
present because of _________________________ ( Fig. 24-9)

Answer 15

sympathetic overstimulation of the levator palpebrae superioris

Question 16

However, true thyroid ophthalmopathy associated with proptosis is seen only in ____________________ (see below).

Answer 16

Graves
disease

Question 17

A person with hyperthyroidism.

A wide-eyed, staring gaze, caused by
overactivity of the sympathetic nervous system, is one of the features of this disorder. In_______________, one of the most important causes ofhyperthyroidism, accumulation of loose
connective tissuebehind the eyeballs,also adds to the protuberant appearance of the eyes.

Answer 17

Graves disease

Question 18

In the gastrointestinal system, sympathetic hyperstimulation of the gut results in__________________

Answer 18

hypermotility,
malabsorption, and diarrhea.

Question 19

The skeletal system is also affected.

• *Thyroid hormone stimulates bone resorption**, increasing
• *porosity of cortical bone** and reducing the volume of trabecular bone.

The net effect is
_____________and an increased risk of fractures in patients with chronic hyperthyroidism.

Answer 19

osteoporosis

Question 20

Other findings include atrophy of skeletal muscle, with fatty infiltration and focal interstitial
lymphocytic infiltrates;minimal liver enlargementdue tofatty changes in the hepatocytes; and
generalized lymphoid hyperplasia and lymphadenopathy in patients with Graves disease.

Question 21

_______________ is used to designate the abrupt onset of severe hyperthyroidism.

This condition
occurs most commonly in patients with underlying Graves disease and probably results from an
acute elevation in catecholamine levels, as might be encountered duringinfection, surgery,
cessation of antithyroid medication,or any form ofstress.

Patients are often febrile and present
with tachycardia out of proportion to the fever.

This is a medical emergency: A
significant number of untreated patients die of cardiac arrhythmias.

Answer 21

Thyroid storm

Question 22

____________________ refers to thyrotoxicosis occurring in the elderly, in whom advanced
age and various co-morbidities may blunt the typical features of thyroid hormone excess seen
in younger patients.

The diagnosis of thyrotoxicosis in these individuals is often made during
laboratory work-up for unexplained weight loss or worsening cardiovascular disease.

Answer 22

Apathetic hyperthyroidism

Question 23

A diagnosis of hyperthyroidism is made using both clinical and laboratory findings.

The measurement of serum________________ provides the most useful single screening test for hyperthyroidism, since its levels are decreased even at the earliest stages, when the disease may still be subclinical.

Answer 23

TSH concentration using sensitive TSH assays

Question 24

A low TSH value is usually confirmed with
__________________, which is expectedly increased.

In an occasional patient,** hyperthyroidism results predominantly** from increased circulating levels of T3 (“T3 toxicosis”).

Answer 24

measurement of free T4

Question 25

In an occasional patient,
hyperthyroidism results predominantly from increased circulating levels of T3 (“T3 toxicosis”).

In these cases,_____________________

Answer 25

** free T4 levels may be decreased, and direct measurement of serum T3 may be
useful**.

Question 26

In rare cases of pituitary-associated (secondary) hyperthyroidism, TSH levels are either
normal or raised.

Determining TSH levels after the injection of __________________ is used in the evaluation of cases of suspected hyperthyroidism with
equivocal changes in the baseline serum TSH level.

Answer 26

• *thyrotropin-releasing hormone**
• *(TRH stimulation test)**

Question 27

A normal rise in TSH after administration of
TRH excludes ______________.

Answer 27

secondary hyperthyroidism

Question 28

Once the diagnosis of thyrotoxicosis has been
confirmed by a** combination of TSH assays and free thyroid hormone level**s,_______________________ by the thyroid gland may be valuable in determining the etiology.

Answer 28

measurement of
radioactive iodin e uptake

Question 29

In measurement of
radioactive iodine uptake

there may be diffusely increased uptake in the whole gland __________________,

Answer 29

Graves’ disease

Question 30

In measurement of
radioactive iodine uptake

increased uptake in a solitary nodule_____________,

Answer 30

(toxic adenoma)

Question 31

In measurement of
radioactive iodine uptake

decreased uptake _______________

Answer 31

(thyroiditis).

Question 32

The therapeutic options for hyperthyroidism include

Answer 32

• multiple medications, each of which has a different mechanism of action.
• Typically, these include a β-blocker to control symptoms induced by increased adrenergic tone,
• a thionamide to block new hormone synthesis,
• an iodine solution to block the release of thyroid hormone,
• and agents that inhibit peripheral conversion of T4 to T3. Radioiodine, which is incorporated into thyroid tissues, resulting in ablation of thyroid function over a period of 6 to 18 weeks, may also be used.