ENDOCRINE DISORDERS-THYROID DISORDERS 1.1 (AB) Flashcards
Which glands are interrelated in thyroid physiology during pregnancy?
Maternal and fetal thyroid glands.
What hormone does the hypothalamus secrete to stimulate TSH production?
Thyrotropin-releasing hormone (TRH).
Which cells in the anterior pituitary secrete TSH?
Thyrotrope cells.
What is the central hormone in screening and diagnosing thyroid disorders?
Thyroid-stimulating hormone (TSH).
Does TSH cross the placenta?
No, TSH does not cross the placenta.
What hormone stimulates TSH production during pregnancy, particularly at 12 weeks AOG?
Human chorionic gonadotropin (hCG).
What secretes hCG?
The placenta.
When does hCG production start?
During implantation, after trophoblastic invasion.
Does hCG production start immediately after fertilization?
No, it begins during implantation.
Why does the thyroid gland enlarge during pregnancy?
Due to granular hyperplasia and increased thyroid hormone production.
What causes an increase in thyroid-binding globulin (TBG) concentration during pregnancy?
Increased hepatic synthesis due to elevated estrogen production.
What effect does elevated TBG have on thyroid hormones?
Increases total T3 and T4 concentration.
What is the role of free T4 in TSH secretion?
Free T4 suppresses TRH, limiting TSH secretion via negative feedback.
When does total serum T4 regress sharply during pregnancy?
At 6-9 weeks AOG.
What organ produces TBG?
The liver.
What happens if circulating T3 and T4 levels are high?
Negative feedback to the hypothalamus suppresses TSH production.
How many thyrocyte components are targeted by autoantibodies in autoimmune thyroid disease?
Approximately 200.
What are the effects of autoantibodies in thyroid disease?
Stimulation, blocking, or inflammation of thyroid function.
What can thyroid inflammation lead to?
Follicular cell destruction.
What is another name for thyroid-stimulating autoantibodies?
Thyroid-stimulating immunoglobulins (TSIs).
What is the primary function of thyroid-stimulating immunoglobulins (TSIs)?
Bind and activate TSH receptors, leading to hyperfunction and growth.
In which disease are thyroid-stimulating immunoglobulins (TSIs) predominantly found?
Graves’ disease.
What are thyroid-stimulating blocking antibodies?
Antibodies that counteract TSIs and may blunt their effect.
What enzyme do thyroid-peroxidase (TPO) antibodies target?
Thyroid-peroxidase (TPO), essential for hormone production.
What is the prevalence of TPO antibodies in pregnancy?
5-15% of pregnancies.
What pregnancy complications are associated with TPO antibodies?
Early pregnancy loss, preterm birth, and placental abruption.
What postpartum conditions are associated with TPO antibodies?
Postpartum thyroid dysfunction and long-term thyroid failure.
What is fetal microchimerism?
Stem cell interchange between fetus and mother leading to engraftment in maternal tissues.
Why is autoimmune thyroid disease more common in women?
Due to increased fetal-to-maternal cell trafficking.
How long can fetal cells persist in maternal circulation?
More than 20 years.
What thyroid conditions are linked to fetal microchimerism?
Hashimoto’s and Graves’ disease.
What is the incidence of hyperthyroidism in pregnancy?
0.4-1.7% of pregnancies.
What are the clinical signs of hyperthyroidism in pregnancy?
Tachycardia, thyromegaly, exophthalmos, and failure to gain weight despite adequate food intake.
What are the key laboratory findings in hyperthyroidism?
Markedly depressed TSH, elevated free T4, and abnormally high serum T3 levels.
What is the hallmark lab pattern in hyperthyroidism?
↓ TSH, ↑ FT4.
What is the hallmark lab pattern in hypothyroidism?
↑ TSH, ↓ FT4.
What is the hallmark lab pattern in subclinical hyperthyroidism?
↓ TSH, normal FT4.
What is the hallmark lab pattern in subclinical hypothyroidism?
↑ TSH, normal FT4.
What is the first test to request when suspecting thyroid pathology?
TSH test.
What additional test should be requested if TSH is low?
Free T4 (FT4) to gauge thyrotoxicosis severity.
What is the most common cause of thyrotoxicosis in pregnancy?
Graves’ disease.
What type of antibodies are associated with Graves’ disease?
Thyroid-stimulating TSH-receptor antibodies.
How do hyperthyroid symptoms change during pregnancy?
Symptoms may worsen initially due to hCG stimulation but diminish in the second half of pregnancy.
What scoring system is used to predict thyroid storm in hyperthyroid patients?
Burch-Wartofsky Score.
What symptoms are considered in the Burch-Wartofsky Score?
Fever, diarrhea, agitation, atrial fibrillation, and congestive heart failure.
What is a thyroid storm?
A life-threatening complication of severe hyperthyroidism.
What is the preferred treatment for thyrotoxicosis in pregnancy?
Thionamide drugs.
What is the preferred antithyroid drug in the first trimester?
Propylthiouracil (PTU).
Why is PTU preferred in the first trimester?
It crosses the placenta less readily than methimazole.
What is the preferred antithyroid drug in the second and third trimesters?
Methimazole.
What congenital anomaly is associated with methimazole use in early pregnancy?
Aplasia cutis (scalp defects).
What are common side effects of antithyroid drugs?
Transient leukopenia, agranulocytosis, hepatotoxicity, allergic rash.
What fetal complications can occur with antithyroid drug use?
Congenital anomalies or postnatal thyroid dysfunction.
What is the recommended PTU dose in pregnancy?
50-150 mg orally three times daily.
What is the recommended methimazole dose in pregnancy?
10-20 mg initially, then 5-10 mg maintenance.
When is thyroidectomy recommended in pregnancy?
In the second trimester if thyrotoxicosis is not controlled by medication.
What are the risks of thyroidectomy during pregnancy?
Parathyroid gland resection, recurrent laryngeal nerve injury.
Is radioactive iodine therapy safe in pregnancy?
No, it is contraindicated due to fetal thyroid gland destruction.
What is the management if a pregnant patient is inadvertently exposed to radioactive iodine?
Evaluate the fetus carefully.
What is the main factor determining pregnancy outcomes in thyroid disorders?
Metabolic control
What pregnancy complications are associated with excess thyroxine?
Miscarriage and preterm birth
What neurological conditions in children are linked to maternal hyperthyroidism?
Epilepsy and autism spectrum disorders
Why are mothers with hyperthyroidism prone to preeclampsia?
Thyroid hormone mimics the alpha subunit of hCG, affecting TSH levels
What are the three maternal outcomes of hyperthyroidism in pregnancy?
Preeclampsia, Heart Failure, Death (PHD)
Why does hyperthyroidism lead to heart failure?
Tachycardia damages cardiac muscle, leading to cardiomyopathy and heart failure
What is the most common fetal thyroid status in maternal hyperthyroidism?
Euthyroid
What are the possible fetal thyroid effects of maternal hyperthyroidism?
Hyperthyroidism, hypothyroidism (with or without goiter)
What percentage of neonates born to mothers with Graves’ disease develop hyperthyroidism?
0.01
What are the fetal/neonatal effects of excessive maternal thyroxine?
Goitrous thyrotoxicosis, goitrous hypothyroidism, non-goitrous hypothyroidism, fetal thyrotoxicosis after maternal thyroid ablation
What is the best predictor of fetal goitrous thyrotoxicosis?
Presence of thyroid-stimulating TSH-receptor antibodies
What is the recommended screening for TRAb in pregnant women?
Routine evaluation in early pregnancy, with repeat testing at 18-22 weeks if elevated
What is the treatment for fetal thyrotoxicosis?
Increased maternal thionamide drugs
What is the management of secondary maternal hypothyroidism to protect the fetus?
Reduced maternal antithyroid medication dose, intraamniotic thyroxine if necessary
What is the recommended fetal thyroid evaluation method?
Umbilical cord blood sampling if fetal goiter is detected
What are the triggers for thyroid storm in pregnancy?
Preeclampsia, anemia, sepsis
What is the management of thyroid storm in pregnancy?
ICU care, thionamides, iodine, dexamethasone, β-blockers
What condition is associated with transient biochemical hyperthyroidism in early pregnancy?
Hyperemesis gravidarum
What causes hyperthyroidism in gestational trophoblastic disease?
Elevated hCG overstimulates TSH receptors
What is the treatment for hyperthyroidism in gestational trophoblastic disease?
Thyroid levels normalize after molar evacuation
How is subclinical hyperthyroidism defined?
Low TSH with normal T4
How is subclinical hypothyroidism defined?
High TSH with normal T4
What is the prevalence of subclinical hyperthyroidism in pregnancy?
0.0177
What is the clinical significance of subclinical hyperthyroidism in pregnancy?
No significant association with adverse pregnancy outcomes
What is the recommended management of subclinical hyperthyroidism in pregnancy?
No treatment, periodic monitoring
