Hormonal involvement in development Flashcards
How do structured become more complex during growth and development t
Morphogenesis and differentiation
What does fetal growth depend on
Genetics of the fetus
Availability of nutrients and oxygen to the fetus
Maternal nutrition
Presence of environmental influences
Various hormones of maternal, fetal and placental origin
Various growth factors of maternal, fetal and placental origin
What play a role in growth and differentiation
Growth hormone (IGFs)
Insulin (a growth hormone)
Thyroid hormones
Glucocorticoids
Role of Foetal growth hormone on prenatal growth
NO direct effect
Absence of fetal growth deficiencies in congenital hypopituitarism
Role of IGFs (Insulin like growth factors) in foetal development
They are mitogenic, stimulating foetal metabolism and coordinating feto-placental metabolism
Role of IGF1
Role of IGF 2
1- regulates early embryonic development
2-responsible for growth of newborn
Role of fetal insulin in development
Indirect role in regulation of fetal growth. Modulates expression of the fetal IGFs. Hyperinsulinelia behind macrosomia
Direct effects on adipose tissue and the proliferation of the cells within the fetus. Fetus therefore becomes bigger. Risk of hypoxia and birth trauma
When is IGF2 more abundant than IGF1
During mid to late gestation
What are the circulating concentrations of IGFs reduced by
Undernutrition and deficiency of:
- Insulin
- Thyroxine
- Glucocorticoids
What does a reduced circulating conc of IGs do
Uptake and utilisation of nutrients.
- Constitutive drive for intrauterine growth (IGF2 plays a key role in placental growth and nutrient transfer)
- Fetal growth in relation to nutrient supply (IGF1 stimulates fetal growth when nutrients are available)
What are thyroid hormones critical for
Development of fetal and neonatal brain and other aspects of pregnancy and fetal growth
What can hypothyroidism in mother of fetus lead to
Fetal disease. This includes a high incidence of lowering IQ, impaired psychomotor development
What do fetal glucocorticoids affect and how
Tissue differentiation and prenatal maturation of organs:
Lungs- maturation of surfactant
Liver- Control of glycaemia
Intestines- Maturation of the expression of digestive enzymes and proliferation of the villi
How is maternal thyroid function altered during pregnancy
Thyroid stimulation is by chorionic gonadotropin
- Placenta secretes huge amounts of hCG which is similar to TSH
- hCG can use TSH receptor on thyroid epithelial cells . Significant fraction of thyroid stimulating activity is from hCG
- Blood levels of TSH are suppressed
- Thyroid stimulating activity of hCG causes some women to develop transient hyperthyroidism (reversible)
How can the effects of thyroid stimulating activity of hCG be prevented
Adequate thyroxine medication
What is the net effect of pregnancy on the thyroid gland
Increased demand. IN normal individuals, not appear to represent much of a load to the thyroid gland, but in females with subclinical hypothyroidism, extra demands of pregnancy can precipitate clinical disease
Does gestational hyperthyroidism as a result of increased levels of HCG need treatment and why
No
IT is transient
Effects of hyperthyroidism on pregnancy
HEart failure
PRe-eclampsia
-Gestational diabetes
-Preterm delivery
Effects of hyperthyroidism on fetus
Increased risk of neonatal mortality
IUGR
Low birth rate
Stillbirth
How does maternal thyroid function increase the demand for iodine
1) Oestrogens stimulate expression of T4 binding globulin in liver
2) Lowered free T4 concentrations- elevated TSH secretion by the pituitary
3) Significant increase in total T4 and T3 levels
Leads to increased demand for iodine. Significant pregnancy associated increase in iodine clearance by the kidney (Increased GFR)
What does the WHO recommend for iodine intake during pregnancy
TO at leat 200 ug/day
What is isolated maternal hypothyroidism associated with
Infertility
-when pregnancy does occur, there is increased risk of intrauterine fetal death and gestational hypertension
How is subclinical hypothyroidism a cause of developmental disease
Caused by autoimmune disease
-Anti-thyroid antibodies cross the placenta. Passive Immune attack on the fetal thyroid gland
Isolated fetal hypothyroidism problems
Most children born with this are normal at birth. Must treat very shortly after birth. If not, child will become permanently mentally and growth retarded (cretinism)
