Endocrinology: Physiological Adaptations to Pregnancy Flashcards
1
Q
Hypothalamic-pituitary-gondal axis
A
- Complex hormonal system
- Involved in regulation of reproductive function in mammals
- Consists of hypothalamus, pituitary gland and gonads (testes and ovaries)
- GnRH (gonadotropin releasing hormone) is released by the hypothalamus into the portal system; stimulates release of gonadotropins from pituitary gland
- LH (luteinising hormone) and FSH (follicle-stimulating hormone) released by pituitary: LH stimulates testes to produce testosterone, ovaries to produce estrogen/ progesterone, trigger ovulation; FSH supports spermatogenesis and follicle development in ovaries/ production of estrogen
- Gonads respond to gonadotropins (LH and FSH) to produce sex hormones (testosterone, estrogen, progesterone) and release eggs during ovulation
2
Q
Hormonal changes during the menstrual cycle if fertilisation doesn’t occur
A
Luteal phase of menstrual cycle: days 14-28
- Corpus luteum is a progesterone factory with a limited life span
- Progesterone induces endometrial secretory phase
- Endometrium (thick and secreting) required for implantation
- If no fertilisation, no need for implantation and no need for endometrium: progesterone decreases, endometrium becomes ischaemic and lost
3
Q
Hormonal changes during the menstrual cycle if fertilisation occurs
A
- Zygote formed, begins dividing
- Implants into uterus around 6-7 days after fertilisation (up to 10 days post-ovulation)
- Need secretory endometrium
- Therefore, need progesterone
- Levels stay high until end of gestation
- Uterus: maintains endomentrium, decreases contraction of myometrial cells (important for quiescence vs. labour)
- Lung: increases tidal volume
- Breast: preparation for lactation
- GIT: smooth muscle relaxation
- Bone marrow: increase erythropoiesis
- Kidney: natriuretic properties (offset by aldosterone
- Corpus luteum is ‘rescued’ by human chorionic gonadotrophin (hCG)
- Glycoprotein synthesised by zygote – even before implantation
- Placental (trophoblast) cells produce and release hCG into maternal circulation
- ‘Tells’ corpus luteum to continue making progesterone and oestrogens (which it does until ~ wk8), then placenta take over production of progesterone and oestrogens
4
Q
Hormonal changes during the menstrual cycle (regardless of whether fertilisation occurs or not)
A
- Oestrogens
- Regulates secretion of progesterone by placenta
- Vital for development of foetus
- Stimulates hypertrophy of myometrial and placental cells
- Stimulates breast development
- Human placental lactogen (hPL)
- Also called human chorionic somatotropin (hCS)
- Lactogenic and diabetogenic: decreases maternal glucose utilisation
- Relaxin
- Produced by corpus luteum and placenta
- Mediates hemodynamic changes (increase cardiac output, arterial compliance and renal blood flow)
- Relaxes pelvic ligaments and softens cervix
- Insulin
- Decrease in sensitivity (insulin resistance) in 2nd half due to increased cortisol, prolactin and human placental lactogen
- High plasma insulin levels, normal to high plasma glucose
- Thyroid axis
- Increase total T3 and T4: hCG exerts some ‘TSH like’ activity
- Increase free (active) T3 and T4 due to oestrogen, increasing TBG
- Aldosterone and corticosteroids
- Adrenal cortical hormones elevated during pregnancy
- Stimulate sodium (and water) retention; expansion of ECF
- Prolactin
- Secreted by the anterior pituitary
- Preparation of breast for lactation (hypertrophy of alveoli)
- Stimulation of milk production postpartum
- Calcitriol (activated vitamin D)
- Calcium demand increased
- Calcitriol increases calcium absorption from intestines
- PTHrp (parathyroid hormone-related peptide)
- Placental hormone
- Mobilises calcium from maternal bones to ensure calcification of the foetal bones
5
Q
Plasma and extracellular fluid changes during pregnancy
A
- ~50% increase in plasma and ECF
- Includes sequestering of sodium in placenta and amnion
- Mediated by increased aldosterone and cortisol (opposed by progesterone and atrial natriuretic peptide)
- Oedema clinically identifiable in 50% of pregnancies
- Hypothalamic osmostat is ‘reset’: thirst increased at lower than usual osmolarity, helps protect lower osmolarity
- Increased water reabsorption: decrease plasma oncotic pressure (due to dilution of plasma protein conc), increased hydrostatic (venous) pressure, contributes to oedema
6
Q
Haematological changes during pregnancy
A
- Erythropoiesis (RBC production) increases: not as much as plasma volume decreased haematocrit, Hb conc normal
- Increased fibrinogen and clotting factors
- Decreased endogenous anticoagulants
- Helps to stop bleeding after delivery but increases risk of thrombosis and thromboembolism (further increased by venous stasis due to vasodilation and compromised venous return)
- Mild haemodilution is normal in pregnancy
7
Q
Cardiac physiology changes during pregnancy
A
- Cardiac output increased by 30-50%
- Heart rate increases by 15 beats/ min
- Stroke volume increases by 10%
- Often heart murmurs can be heard due to increased blood flow through heart, altered heart configuration, mammary vessels: difficult to distinguish on auscultation from those due to significant cardiac or vascular disease
8
Q
BP changes during pregnancy
A
- Increased CO, decreased vascular resistance
- Same systolic pressure, decreased diastolic pressure during 1st half by ~15mmHg
- Due to peripheral vasodilation
- Mediated by progesterone, prostaglandin E2 and prostacyclin; increased NO production
- Triggers volume expansion (via RAAS)
9
Q
Renal physiology changes during pregnancy
A
- Increased GFR (up 50% by end of first trimester)
- Increased renal plasma flow: decreased pre- and post-glomerular resistance
- Decreased plasma urea and creatinine (increased clearance)
- Microalbuminuria (due to haemodynamic, permeability and tubular reabsorption changes)
- Glucosuria (glucose in urine): increased filtration rate of glucose, impaired reabsorption, may increase chances of UTI
10
Q
Respiratory physiology changes during pregnancy
A
- Progesterone increasing sensitivity of respiratory centre to CO2
- Increase tidal volume x respiratory rate = increase minute ventilation; helps meet increased O2 demand
- Keeping maternal pCO2 low encourages CO2 removal from foetus
- Renal excretion of HCO3- maintains normal pH
- Breathlessness (dyspnoea) not unusual
- Lung volume changes
- Increased tidal volume
- Expiratory reserve volume and functional residual capacity (FRC) decrease
- The enlarging uterus can elevate the diaphragm by as much as 4cm the transverse chest diameter can be increased by 2cm
11
Q
Gastrointestinal system changes during pregnancy
A
- Taste often altered
- Reduced gastric secretion
- Delayed gastric emptying
- Reduced gut motility; constipation
- Nausea and vomiting common (~50% of pregnancies)
12
Q
How do pregnancy hormones affect the brain?
A
- Oestrogen and progesterone: enlarge cell bodies of neurons of the medial preoptic area of the hypothalamus (maternal behaviour), increase SA of neuronal branches in the hippocampus (memory and learning)
- Oxytocin: stimulates the hippocampus
13
Q
How can pregnancy cause insomnia?
A
- Increased awareness of foetal movements at rest
- Feeling too hot due to peripheral vasodilation
- Nocturia
14
Q
How can pregnancy darken skin?
A
- Hyperpigmentation occurs due to increased secretion of melanocyte stimulating hormone (MSH) – from pars intermedia of pituitary gland
- Promotes linea nigra (dark line down abdomen), darkening of areola, facial chloasma/ melasma ‘pregnancy mask’
15
Q
Impacts on pregnancy on oral health
A
- Vomiting (morning sickness) can contribute to enamel erosion
- Changes in feeding habits (grazing, food fads), decreased oral hygiene (tiredness, nausea) and reduced dental visits can be detrimental for dental health
- Pregnancy gingivitis: usually in 2nd trimester; hormonal excesses causes gums to react differently to bacteria. Periodontitis has been linked to preterm labour (increase prostaglandins)
- Pyogenic granuloma (pregnancy tumours); rare, inflammatory, benign growths that develop on the gums as part of an exaggerated response to plaque. Pregnancy tumours usually subside shortly after childbirth
