MLT GlobeChemistry: Endocrinology – page 3
123 Chemistry MCQs on Endocrinology with answers and explanations.
'Adenohypophysis' is another name for which structure?
The adenohypophysis develops from Rathke's pouch and makes GH, PRL, ACTH, TSH, FSH and LH. The posterior pituitary (neurohypophysis) releases ADH and oxytocin.
A 2-year-old has an abdominal mass. Raised urinary HVA and VMA best support which diagnosis?
Neuroblastomas make dopamine and noradrenaline, so HVA and VMA rise. Phaeochromocytoma is usually a tumour of adults and is detected with metanephrines.
Which factor suppresses ACTH secretion by the anterior pituitary?
Cortisol gives negative feedback to the hypothalamus (CRH) and pituitary (ACTH). Stress, hypoglycaemia and the morning circadian peak increase ACTH.
Which condition raises total T4 by increasing TBG?
Estrogen increases TBG synthesis and sialylation. Nephrotic syndrome (urinary loss), androgens and acute illness lower TBG or its binding.
A patient's thyroid panel shows high free T4 caused by a hormone-secreting thyroid adenoma. What TSH result is expected?
Excess thyroid hormone from the gland itself (primary hyperthyroidism) exerts negative feedback on the pituitary, suppressing TSH. Raised TSH points to primary hypothyroidism or a TSH-secreting pituitary lesion.
A young woman with weight loss, tremor and exophthalmos has suppressed TSH, high free T4 and positive TSH-receptor antibodies. The diagnosis is:
TSH-receptor stimulating antibodies drive the thyroid in Graves disease, raising T4 and suppressing TSH. Eye disease is specific to Graves.
Which result pattern defines subclinical hypothyroidism?
Subclinical hypothyroidism is a raised TSH with free T4 still in the reference interval. Low TSH with normal free T4 and T3 is subclinical hyperthyroidism.
Which antibody is most useful for confirming autoimmune (Hashimoto) thyroiditis?
Anti-TPO antibodies are present in most patients with Hashimoto thyroiditis. TSH-receptor antibodies are characteristic of Graves disease.
A patient with fatigue and hyperpigmentation has low morning cortisol and very high ACTH. The most likely diagnosis is:
Adrenal gland failure removes cortisol negative feedback, so ACTH rises; high ACTH (with POMC-derived MSH activity) causes pigmentation. Secondary insufficiency has low ACTH and no pigmentation.
Anti-Müllerian hormone (AMH) is mainly used to assess:
AMH is made by granulosa cells of small growing follicles and reflects the remaining follicle pool. It is used in fertility assessment and falls towards menopause.
Which test best reflects a person's vitamin D stores?
25-hydroxyvitamin D has a long half-life and reflects intake and skin production. 1,25-dihydroxyvitamin D is tightly regulated and may be normal or high in deficiency.
In a normal early intrauterine pregnancy, serum hCG approximately doubles every:
In early viable intrauterine pregnancy, hCG roughly doubles every 48 hours (about 48-72 h) during the first weeks. The rate of rise slows after about 6-7 weeks, and hCG peaks at about 8-10 weeks before falling. A rise that is too slow may suggest ectopic or failing pregnancy.
In a healthy person with a normal sleep pattern, serum cortisol is highest:
Cortisol follows a circadian rhythm, peaking around waking and reaching its lowest level near midnight. This is why morning samples are used to assess adrenal insufficiency.
How do steroid hormones such as cortisol mainly act on target cells?
Steroids are lipid-soluble, cross the membrane and bind cytoplasmic or nuclear receptors that act as transcription factors. Peptide hormones use cell-surface receptors and second messengers.
Which thyroid hormone is secreted in the largest amount by the thyroid gland?
The thyroid secretes mainly T4; most circulating T3 is formed from T4 in peripheral tissues. T3 is the more active hormone.
The main action of prolactin is to:
Prolactin from the anterior pituitary stimulates milk production by the breast. Oxytocin causes uterine contraction and milk ejection.
Antidiuretic hormone (ADH) is stored and released from the:
ADH is made in the hypothalamus and stored in and released from the posterior pituitary (neurohypophysis).
Urine and serum pregnancy tests detect which hormone?
hCG is produced by the trophoblast soon after implantation, and immunoassays for hCG are the basis of pregnancy tests.
Cortisol is produced by the:
Cortisol is made in the zona fasciculata of the adrenal cortex under ACTH control. The adrenal medulla makes catecholamines.
Which hormone raises blood calcium?
PTH raises blood calcium by releasing calcium from bone, increasing renal reabsorption and stimulating calcitriol formation. Calcitonin lowers calcium.